Professor of Medicine (Cardiovascular Medicine) at the Stanford University Medical Center

Medicine - Cardiovascular Medicine

Bio

Bio

Dr. Wang is the Director of the Stanford Cardiac Arrhythmia Service and Professor of Medicine and of Bioengineering (by courtesy)(since 2003). Dr. Wang is an expert in the treatment of cardiac arrhythmias, including atrial fibrillation, atrial flutter, ventricular arrhythmias, supraventricular arrhythmias, and sudden cardiac death. He has practiced cardiac electrophysiology as an arrhythmia expert for over 26 years. He was a co-inventor of catheter cryoablation, which has been used to treat over 250,000 patients with atrial fibrillation, and has pioneered new techniques in the management of heart rhythm problems. He has co-authored numerous textbooks and book chapters on catheter ablation, implantable defibrillators, sudden cardiac death, cardiac resynchronization/ biventricular pacing therapy, and innovations in arrhythmia therapy. He is past Chair of the American Heart Association Council on Clinical Cardiology ECG and Arrhythmias Committee, a member of the American Heart Association Council on Clinical Cardiology, and the American Heart Association National Science and Clinical Education Committee. He is a former member of the Board of Trustees of the leading professional society in his field, the Heart Rhythm Society. He has helped write the examination used for certification of heart rhythm specialists in the U.S. He founded the annual Stanford Biodesign New Arrhythmia Technologies Retreat, focusing on new technological advances in arrhythmia management and diagnosis. He serves as the Editor-in-Chief of Circulation:Arrhythmia and Electrophysiology, one of the leading scientific journals in the field.

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Research & Scholarship

Current Research and Scholarly Interests

Dr. Wang's research centers on the development of innovative approaches to the treatment of arrhythmias, including more effective catheter ablation techniques, more reliable implantable devices, and less invasive treatments. Dr. Wang's clinical research interests include atrial fibrillation, ventricular tachycardia, syncope, and hypertrophic cardiomyopathy. Dr. Wang has active collaborations with Bioengineering, Mechanical Engineering, and Electrical Engineering Departments at Stanford. Some of the goals of his research program are: 1) to create a more effective methods of catheter ablation, 2) to create implantable pacemakers and leads that are more reliable, 3) to create a combined surgical-catheter approach to ablation, 4) to create noninvasive methods of ablation, 5) to make defibrillation painless.

Clinical Trials

The (Catheter Ablation Versus Anti-arrhythmic Drug Therapy for Atrial Fibrillation Trial)
CABANA Trial has the overall goal of establishing the appropriate roles for medical and
ablative intervention for atrial fibrillation (AF). The CABANA Trial is designed to test the
hypothesis that the treatment strategy of left atrial catheter ablation for the purpose of
eliminating atrial fibrillation (AF) will be superior to current state-of-the-art therapy
with either rate control or rhythm control drugs for decreasing the incidence of the
composite endpoint of total mortality, disabling stroke, serious bleeding, or cardiac arrest
in patients with untreated or incompletely treated AF.

Stanford is currently not accepting patients for this trial.For more information, please contact Linda Norton, (650) 725 - 5597.

This is a prospective randomized study to assess the safety and efficacy of FIRM (Focal
Impulse and Rotor Modulation)-guided ablation for the treatment of symptomatic atrial
fibrillation (AF). The study hypothesis is that the efficacy of AF elimination at 1 year will
be higher by ablating patient-specific AF-sustaining rotors and focal sources by Focal
Impulse and Rotor Modulation (FIRM) compared to conventional ablation alone (wide-area PV
isolation).

Abstract

Mechanisms for persistent atrial fibrillation (AF) are unclear. We hypothesized that putative AF drivers and disorganized zones may interact dynamically over short time scales. We studied this interaction over prolonged durations, focusing on regions where ablation terminates persistent AF using 2 mapping methods.We recruited 55 patients with persistent AF in whom ablation terminated AF prior to pulmonary vein isolation from a multicenter registry. AF was mapped globally using electrograms for 360±45 cycles using (1) a published phase method and (2) a commercial activation/phase method.Patients were 62.2±9.7 years, 76% male. Sites of AF termination showed rotational/focal patterns by methods 1 and 2 (51/55 vs 55/55; P=0.13) in spatially conserved regions, yet fluctuated over time. Time points with no AF driver showed competing drivers elsewhere or disordered waves. Organized regions were detected for 61.6±23.9% and 70.6±20.6% of 1 minute per method (P=nonsignificant), confirmed by automatic phase tracking (P<0.05). To detect AF drivers with >90% sensitivity, 8 to 32 s of AF recordings were required depending on driver definition.Sites at which persistent AF terminated by ablation show organized activation that fluctuate over time, because of collision from concurrent organized zones or fibrillatory waves, yet recur in conserved spatial regions. Results were similar by 2 mapping methods. This network of competing mechanisms should be reconciled with existing disorganized or driver mechanisms for AF, to improve clinical mapping and ablation of persistent AF.URL: http://www.clinicaltrials.gov. Unique identifier: NCT02997254.

Abstract

Discordant and concordant left bundle branch block (dLBBB/cLBBB) are characterized by negative or positive T waves, respectively, in lateral leads. We assessed if the two morphologies are associated with different clinical status and prognosis in patients with heart failure (HF) and current indication to Cardiac Resynchronization Therapy (CRT)/CRT-Defibrillator (CRT-D).Baseline electrocardiograms of 1270 patients with LBBB in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy cohort were analysed to identify dLBBB and cLBBB. The two groups were compared with respect to baseline clinical characteristics, primary endpoint (HF event or death), and secondary endpoint (ventricular tachycardia, ventricular fibrillation, or death) over a 3.5-year period, and benefit of CRT-D over implantable cardioverter defibrillator (ICD). dLBBB was identified in 909 (72%) patients, and cLBBB in 361 (28%). Patients with dLBBB were older, had more severe symptoms and systolic dysfunction, as well as higher brain natriuretic peptide. CRT-D was superior to ICD in patients with both LBBB morphologies. The occurrence of the primary outcome was significantly more frequent in patients with dLBBB than in those with cLBBB, both in the entire cohort (P = 0.005), and in the CRT-D arm (P = 0.002). There was a trend towards more frequent occurrence of the secondary endpoint in patients with dLBBB than in those with cLBBB, but statistical significance was not reached in the whole population or in the subgroup undergoing CRT-D. Among patients receiving CRT-D, dLBBB was an independent predictor of the primary endpoint.dLBBB morphology is associated with more severe HF clinical status and worse prognosis, even in patients receiving CRT-D, compared with cLBBB morphology.

Abstract

Pulmonary vein isolation (PVI) via catheter ablation is an approved therapy for patients with drug-refractory and symptomatic atrial fibrillation (AF). Furthermore, cryoballoon is now considered to be as effective as focal radiofrequency catheter ablation. This study examines the second-generation cryoballoon performance in a US multicenter review of real-world practices.By retrospective chart collections, the long-term efficacy and safety of the cryoballoon procedure were assessed in 15 US centers. All patients had a history of drug-refractory symptomatic paroxysmal AF and were treated with a cryoballoon PVI strategy at the index ablation.Four hundred fifty-two patients were evaluated, and acute PVI was achieved in 99% of patients by cryoballoon catheter ablation. In 0.88% of patients (4/452), an additional focal ablation catheter was used to achieve acute PVI during the ablation procedure. Average procedure time was 128 (range 82 to 260) min, using an average of 17 (range 1 to 19) min of fluoroscopy. The most frequent adverse event was transient phrenic nerve injury (1.5%; 7/452 patients) which all resolved by the end of the procedure with no diaphragmatic dysfunction at discharge. There were no strokes, transient ischemic attacks, cardiac tamponade, atrioesophageal fistulas, or deaths during the study. At the 12-month efficacy endpoint, single-procedure success of freedom from atrial arrhythmia was 87% (393/452 patients).This real-world examination of the US practice demonstrates that second-generation cryoballoon ablation by PVI strategy is safe and effective among patients with paroxysmal AF.

Abstract

The cryoballoon was invented to achieve circumferential pulmonary vein isolation more efficiently to compliment the shortcomings of point-by-point ablation by radiofrequency ablation (RFA). Its efficacy and safety were shown to be comparable to those of RFA, and the clinical outcomes have improved with the second-generation cryoballoon. The basic biophysics, implemental techniques, procedural recommendations, clinical outcomes, and complications of the cryoballoon are presented in this practical and systematic review.

Abstract

OBJECTIVE: To investigate mechanisms by which atrial fibrillation (AF) may terminate during ablation near the pulmonary veins before the veins are isolated (PVI).INTRODUCTION: It remains unstudied how AF may terminate during ablation before PVs are isolated, or how patients with PV reconnection can be arrhythmia-free. We studied patients in whom PV antral ablation terminated AF before PVI, using two independent mapping methods.METHODS: We studied patients with AF referred for ablation, in whom biatrial contact basket electrograms were studied by both an activation/phase mapping method and by a second validated mapping method reported not to create false rotational activity.RESULTS: In 22 patients (age 60.1 ± 10.4, 36% persistent AF), ablation at sites near the PVs terminated AF (77% to sinus rhythm) prior to PVI. AF propagation revealed rotational (n=20) and focal (n=2) patterns at sites of termination by mapping method 1 and method 2. Both methods showed organized sites that were spatially concordant (P<0.001) with similar stability (P<0.001). Vagal slowing was not observed at sites of AF termination.DISCUSSION: PV antral regions where ablation terminated AF before PVI exhibited rotational and focal activation by two independent mapping methods. These data provide an alternative mechanism for the success of PVI, and may explain AF termination before PVI or lack of arrhythmias despite PV reconnection. Mapping such sites may enable targeted PV lesion sets and improved freedom from AF.

Abstract

INTRODUCTION: We performed a systematic review and meta-analysis of geographic and racial representation and reported success rates of studies of catheter ablation for atrial fibrillation (AF).METHODS AND RESULTS: We searched PubMed, Scopus, and Cochrane databases from 1/1/1990 to 8/1/2016 for trials and observational studies reporting AF ablation outcomes. Major exclusion criteria were insufficient reporting of outcomes, non-English language articles, and ablation strategies that were not prespecified and uniform. We described geographic and racial representation and single-procedure ablation success rates by country, controlling for patient demographics and study design characteristics. The analysis cohort included 306 studies (49,227 patients) from 28 countries. Over half of the paroxysmal (PAF) and nonparoxysmal AF (NPAF) treatment arms were conducted in 5 and 3 countries, respectively. Reporting of race or ethnicity demographics and outcomes were rare (1 study, 0.3%) and nonexistent, respectively. Unadjusted success rates by country ranged from 63.5% to 83.0% for PAF studies and 52.7% to 71.6% for NPAF studies, with substantial variation in patient demographics and study design. After controlling for covariates, South Korea and the United States had higher PAF ablation success rates, with large residual heterogeneity. NPAF ablation success rates were statistically similar by country.CONCLUSIONS: Studies of AF ablation have substantial variation in patient demographics, study design, and reported outcomes by country. There is limited geographic representation of trials and observational studies of AF ablation and a paucity of race- or ethnicity-stratified results. Future AF ablation studies and registries should aim to have broad representation by race, geography, and ethnicity to ensure generalizability.

Abstract

The outcomes from pulmonary vein isolation (PVI) for atrial fibrillation (AF) are suboptimal, but the benefits of additional lesion sets remain unproven. Recent studies propose ablation of AF drivers improves outcomes over PVI, yet with conflicting reports in the literature. We undertook a systematic literature review and meta-analysis to determine outcomes from ablation of AF drivers in addition to PVI or as a stand-alone procedure.Database search was done using the terms atrial fibrillation and ablation or catheter ablation and driver or rotor or focal impulse or FIRM (Focal Impulse and Rotor Modulation). We pooled data using random effects model and assessed heterogeneity with I2 statistic.Seventeen studies met inclusion criteria, in a cohort size of 3294 patients. Adding AF driver ablation to PVI reported freedom from AF of 72.5% (confidence interval [CI], 62.1%-81.8%; P<0.01) and from all arrhythmias of 57.8% (CI, 47.5%-67.7%; P<0.01). AF driver ablation when added to PVI or as stand-alone procedure compared with controls produced an odds ratio of 3.1 (CI, 1.3-7.7; P=0.02) for freedom from AF and an odds ratio of 1.8 (CI, 1.2-2.7; P<0.01) for freedom from all arrhythmias in 4 controlled studies. AF termination rate was 40.5% (CI, 30.6%-50.9%) and predicted favorable outcome from ablation(P<0.05).In controlled studies, the addition of AF driver ablation to PVI supports the possible benefit of a combined approach of AF driver ablation and PVI in improving single-procedure freedom from all arrhythmias. However, most studies are uncontrolled and are limited by substantial heterogeneity in outcomes. Large multicenter randomized trials are needed to precisely define the benefits of adding driver ablation to PVI.

Abstract

The mechanisms by which persistent atrial fibrillation (AF) terminates via localized ablation are not well understood. To address the hypothesis that sites where localized ablation terminates persistent AF have characteristics identifiable with activation mapping during AF, we systematically examined activation patterns acquired only in cases of unequivocal termination by ablation.We recruited 57 patients with persistent AF undergoing ablation, in whom localized ablation terminated AF to sinus rhythm or organized tachycardia. For each site, we performed an offline analysis of unprocessed unipolar electrograms collected during AF from multipolar basket catheters using the maximum -dV/dt assignment to construct isochronal activation maps for multiple cycles. Additional computational modeling and phase analysis were used to study mechanisms of map variability. At all sites of AF termination, localized repetitive activation patterns were observed. Partial rotational circuits were observed in 26 of 57 (46%) cases, focal patterns in 19 of 57 (33%), and complete rotational activity in 12 of 57 (21%) cases. In computer simulations, incomplete segments of partial rotations coincided with areas of slow conduction characterized by complex, multicomponent electrograms, and variations in assigning activation times at such sites substantially altered mapped mechanisms.Local activation mapping at sites of termination of persistent AF showed repetitive patterns of rotational or focal activity. In computer simulations, complete rotational activation sequence was observed but was sensitive to assignment of activation timing particularly in segments of slow conduction. The observed phenomena of repetitive localized activation and the mechanism by which local ablation terminates putative AF drivers require further investigation.

Abstract

Cost-effectiveness or value of cardiovascular therapies may be undermined by unwarranted cost variation, particularly for heterogeneous procedures such as catheter ablation for atrial fibrillation (AF). We sought to characterize cost variation of AF ablation in the U.S. health care system and the relationship between cost and outcomes.We performed a retrospective cohort study using data from the MarketScan® commercial claims and Medicare supplemental databases including patients who received an AF ablation from 2007 through 2011. We aggregated encounter cost, reflecting total payments received for the encounter, to the facility level to calculate median facility cost. We classified procedures as outpatient or inpatient and assessed for association between cost and 30-day and one-year outcomes. The analysis cohort included 9,415 AF ablations (59±11 years; 28% female; 52% outpatient) occurring at 327 facilities, with large cost variation across facilities (median: $25,100; 25th percentile: $18,900, 75th percentile: $35,600, 95th percentile: $57,800). Among outpatient procedures, there was reduced health care utilization in higher cost quintiles with reductions in rehospitalization at 30-days (Quintile 1: 16.1%, Quintile 5: 8.8%, p

Abstract

Pulmonary vein isolation (PVI) is central to ablation approaches for atrial fibrillation (AF), yet many patients still have arrhythmia recurrence after one or more procedures, despite evolving technologies for PVI. Ablation of localised AF drivers, which lie outside the pulmonary veins in many patients, is a practical approach that has been shown to improve success by many groups. Such localised drivers lie in atrial regions shown mechanistically to sustain AF in optical mapping and clinical studies of human AF, as well as computational and animal studies. Clinical studies now verify rotational activation by multiple mapping approaches in the same patients, at sites where ablation terminates persistent AF. This review article provides a mechanistic and clinical rationale to ablate localised drivers, and describes successful techniques for their ablation as well as pitfalls to avoid, which may explain discrepancies between results from some centres. We hope that this review will serve as a platform for future improvements in the patient-tailored ablation for complex arrhythmias.

Abstract

This scientific statement provides an interprofessional, comprehensive review of evidence and recommendations for indications, duration, and implementation of continuous electro cardiographic monitoring of hospitalized patients. Since the original practice standards were published in 2004, new issues have emerged that need to be addressed: overuse of arrhythmia monitoring among a variety of patient populations, appropriate use of ischemia and QT-interval monitoring among select populations, alarm management, and documentation in electronic health records.Authors were commissioned by the American Heart Association and included experts from general cardiology, electrophysiology (adult and pediatric), and interventional cardiology, as well as a hospitalist and experts in alarm management. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Authors were assigned topics relevant to their areas of expertise, reviewed the literature with an emphasis on publications since the prior practice standards, and drafted recommendations on indications and duration for electrocardiographic monitoring in accordance with the American Heart Association Level of Evidence grading algorithm that was in place at the time of commissioning.The comprehensive document is grouped into 5 sections: (1) Overview of Arrhythmia, Ischemia, and QTc Monitoring; (2) Recommendations for Indication and Duration of Electrocardiographic Monitoring presented by patient population; (3) Organizational Aspects: Alarm Management, Education of Staff, and Documentation; (4) Implementation of Practice Standards; and (5) Call for Research.Many of the recommendations are based on limited data, so authors conclude with specific questions for further research.

Abstract

Pulmonary vein isolation (PVI) is central to ablation approaches for atrial fibrillation (AF), yet many patients still have arrhythmia recurrence after one or more procedures despite the latest technology for PVI. Ablation of rotational or focal sources for AF, which lie outside the pulmonary veins in many patients, is a practical approach that has been shown to improve success by many groups. Localized sources lie in atrial regions shown mechanistically to sustain AF in optical mapping and clinical studies of human AF, as well as computational and animal studies. Because they arise in localized atrial regions, AF sources may explain central paradoxes in clinical practice - such as how limited ablation in patient specific sites can terminate persistent AF yet extensive anatomical ablation at stereotypical locations, which should extinguish disordered waves, does not improve success in clinical trials. Ongoing studies may help to resolve many controversies in the field of rotational sources for AF. Studies now verify rotational activation by multiple mapping approaches in the same patients, at sites where ablation terminates persistent AF. However, these studies also show that certain mapping methods are less effective for detecting AF sources than others. It is also recognized that the success of AF source ablation is technique dependent. This review article provides a mechanistic and clinical rationale to ablate localized sources (rotational and focal), and describes successful techniques for their ablation as well as pitfalls to avoid. We hope that this review will serve as a platform for future improvements in the patient-tailored ablation for complex arrhythmias.

Abstract

Atrial fibrillation (AF) occurs in many clinical contexts and is diagnosed and treated by clinicians across many specialties. This approach has resulted in treatment variations.The goal of this study was to evaluate the association between treating specialty and AF outcomes among patients newly diagnosed with AF.Using data from the TREAT-AF (Retrospective Evaluation and Assessment of Therapies in AF) study from the Veterans Health Administration, patients with newly diagnosed, nonvalvular AF between 2004 and 2012 were identified who had at least 1 outpatient encounter with primary care or cardiology within 90 days of the AF diagnosis. Cox proportional hazards regression was used to evaluate the association between treating specialty and AF outcomes.Among 184,161 patients with newly diagnosed AF (age 70 ± 11 years; 1.7% women; CHA2DS2-VASc score 2.6 ± 1.7), 40% received cardiology care and 60% received primary care only. After adjustment for covariates, cardiology care was associated with reductions in stroke (hazard ratio [HR]: 0.91; 95% confidence interval [CI]: 0.86 to 0.96; p

Abstract

There are limited data on the prognostic importance of declining activity level in patients with heart failure.We aimed to assess the association of reduced activity level with adverse cardiovascular outcomes in the Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy (MADIT-CRT).Final device interrogations from patients enrolled in the MADIT-CRT with cardiac resynchronization devices capable of recording percent daily activity level were assessed. To determine temporal change, standardized activity levels (SALs) comparing each week to the monthly activity 3 months prior were obtained. Death, heart failure events (HFEs)/death, and ventricular tachyarrhythmias (VTAs)/death were the primary end points of this study.The average absolute activity level and SAL of the final week prior to death or end of study were significantly lower in patients who died compared with those in patients who did not. The total cohort (N = 1008) was further randomized into 2 subgroups to identify (group 1) and validate an optimal threshold (group 2). Patients with >40% reduced SAL had a significantly increased 77-day short-term cumulative incidence of death (P = .0006), HFE/death (P < .0001), or VTA/death (P = .0248). After adjustment for clinical covariates, these patients remained at an increased risk for death (hazard ratio [HR], 2.7; 95% confidence interval [CI], 1.5-4.9; P = .001), HFE/death (HR, 2.7; 95% CI, 1.8-3.9; P ? .001) and VTA/death (HR, 1.9; 95% CI, 1.31-2.6; P = .001). A decline in SAL following a nonfatal VTA and HFE was also associated with an increased probability of death.Decline in activity level is a short-term predictor for adverse cardiovascular events in patients with mild to moderate heart failure undergoing cardiac resynchronization.

Abstract

Focal Impulse and Rotor Modulation (FIRM) uses 64-electrode basket catheters to identify atrial fibrillation (AF)-sustaining sites for ablation, with promising results in many studies. Accordingly, new basket designs are being tested by several groups. We set out to determine the procedural safety of adding basket mapping and map-guided ablation to conventional pulmonary vein isolation (PVI).We collected 30?day procedural safety data in five US centres for consecutive patients undergoing FIRM plus PVI (FIRM-PVI) compared with contemporaneous controls undergoing PVI without FIRM. A total of 625 cases were included in this analysis: 325 FIRM-PVI and 300 PVI-controls. FIRM-PVI patients were more likely than PVI-controls to be male (83% vs. 66%, P?0.001) and have long-standing persistent AF (26% vs. 13%, P?0.001) reflecting patients referred for FIRM. Total ablation time was greater for FIRM-PVI (62?±?22?min) vs. PVI-controls (52?±?18?min, P?=?0.03). The complication rate for FIRM-PVI procedures (4.3%) was similar to controls (4.0%, P?=?1) for both major and minor complications; no deaths were reported. The rate of complications potentially attributable to the basket catheter was small and did not differ between basket types (Constellation 2.8% vs. FIRMap 1.8%, P?=?0.7) or between cases in which basket catheters were and were not used (P?=?0.5). Complication rates did not differ between centres (P?=?0.6).Procedural complications from the use of the basket catheters for AF mapping are low, and thus procedural safety appears similar between FIRM-PVI and PVI-controls in a large multicentre cohort. Future studies are required to determine the optimal approach to maximize the efficacy of FIRM-guided ablation.

Abstract

During ablation for atrial fibrillation (AF), it is challenging to anticipate transitions to organized tachycardia (AT). Defining indices of this transition may help to understand fibrillatory conduction and help track therapy.To determine the timescale over which atrial fibrillation (AF) organizes en route to atrial tachycardia (AT) using the ECG referenced to intracardiac electrograms.In 17 AF patients at ablation (58.7±9.6years; 53% persistent AF) we analyzed spatial loops of atrial activity on the ECG and intracardiac electrograms over successive timepoints. Loops were tracked at precisely 15, 10, 5, 3 and 1min prior to defined transitions of AF to AT.Organizational indices reliably quantified changes from AF to AT. Spatiotemporal AF organization on the ECG was identifiable at least 15min before AT was established (p=0.02).AF shows anticipatory global organization on the ECG minutes before AT is clinically evident. These results offer a foundation to establish when AF therapy is on an effective path, and for a quantitative classification separating AT from AF.

Abstract

A myocardial bridge (MB) has been associated with ventricular arrhythmia and sudden death during exercise. QT dispersion (QTd) is a measure of abnormal repolarization and may predict ventricular arrhythmia. We investigated the frequency of ventricular arrhythmias during exercise and the QTd at rest and after exercise, in patients with an MB compared to a normal cohort.We studied the rest and stress ECG tracings of patients with an MB suspected by focal septal buckling on exercise echocardiography (EE) (Echo-MB group, N = 510), those with an MB confirmed by another examination (MB group, N = 110), and healthy controls (Control group, N = 198).The frequency of exercise-induced premature ventricular contractions (PVCs) was significantly higher in the Echo-MB and MB groups compared with the Control group (both p

Abstract

Atrial fibrillation (AF) often converts to and from atrial tachycardia (AT), but it is undefined if these rhythms are mechanistically related in such patients. We tested the hypothesis that critical sites for AT may be related to regional AF sources in patients with both rhythms, by mapping their locations and response to ablation on transitions to and from AF.From 219 patients undergoing spatial mapping of AF prior to ablation at 3 centers, we enrolled 26 patients in whom AF converted to AT by ablation (n=19) or spontaneously (n=7; left atrial size 42±6cm, 38% persistent AF). Both atria were mapped in both rhythms by 64-electrode baskets, traditional activation maps and entrainment.Each patient had a single mapped AT (17 reentrant, 9 focal) and 3.7±1.7 AF sources. The mapped AT spatially overlapped one AF source in 88% (23/26) of patients, in left (15/23) or right (8/23) atria. AF transitioned to AT by 3 mechanisms: (a) ablation anchoring AF rotor to AT (n=13); (b) residual, unablated AF source producing AT (n=6); (c) spontaneous slowing of AF rotor leaving reentrant AT at this site without any ablation (n=7). Electrogram analysis revealed a lower peak-to-peak voltage at overlapping sites (0.36±0.2mV vs 0.49±0.2mV p=0.03).Mechanisms responsible for AT and AF may arise in overlapping atrial regions. This mechanistic inter-relationship may reflect structural and/or functional properties in either atrium. Future work should delineate how acceleration of an organized AT may produce AF, and whether such regions can be targeted a priori to prevent AT recurrence post AF ablation.

Abstract

The role of atrial fibrillation (AF) substrates is unclear in patients with paroxysmal AF (PAF) that recurs after pulmonary vein isolation (PVI). We hypothesized that patients with recurrent post-ablation (redo) PAF despite PVI have electrical substrates marked by rotors and focal sources, and structural substrates that resemble persistent AF more than patients with (de novo) PAF at first ablation.In 175 patients at 11 centers, we compared AF substrates in both atria using 64 pole-basket catheters and phase mapping, and indices of anatomical remodeling between patients with de novo or redo PAF and first ablation for persistent AF.Sources were seen in all patients. More patients with de novo PAF (78.0%) had sources near PVs than patients with redo PAF (47.4%, p=0.005) or persistent AF (46.9%, p=0.001). The total number of sources per patient (p=0.444), and number of non-PV sources (p=0.701) were similar between groups, indicating that redo PAF patients had residual non-PV sources after elimination of PV sources by prior PVI. Structurally, left atrial size did not separate de novo from redo PAF (49.5±9.5 vs. 49.0±7.1mm, p=0.956) but was larger in patients with persistent AF (55.2±8.4mm, p=0.001).Patients with paroxysmal AF despite prior PVI show electrical substrates that resemble persistent AF more closely than patients with paroxysmal AF at first ablation. Notably, these subgroups of paroxysmal AF are indistinguishable by structural indices. These data motivate studies of trigger versus substrate mechanisms for patients with recurrent paroxysmal AF after PVI.

Abstract

Approximately 10-20% of ICD recipients receive inappropriate device therapies. The purpose of this study was to compare the frequency of inappropriate therapies (IT) between men and women enrolled in MADIT II and MADIT-CRT, and assess for potential adverse outcomes.The electrograms for each ICD or CRT-D therapy, defined as either ATP or shock, were reviewed by adjudication committees for both studies. ICD therapy was considered inappropriate if it was delivered for reasons other than VT/VF. The rhythm triggering IT was categorized as atrial fibrillation/flutter, SVT, or inappropriate sensing when possible.One thousand nine hundred and fifty-four men and 556 women received ICD or CRT-D devices. The risk of IT was significantly lower in women than men (9.2% vs. 13.5%, P = 0.006). The most common cause of IT in men was atrial fibrillation (38%) and SVT in women (43%). Inappropriate shock was not associated with increased mortality in either women (HR 0.82 [95% CI 0.11-6.08]; P = NS) or men (HR 1.37 [95% CI 0.75-2.48]; P = NS) by multivariate analysis. Conversely, appropriate shock therapy strongly correlated with increased risk of death during subsequent post-shock follow-up in women (HR 5.99 [95% CI 2.75-13.02]; P < 0.0001) and men (HR 2.61 [95% CI 1.82-3.74]; P < 0.0001).Women experience significantly less IT than men, partially explained by the increased frequency of atrial fibrillation in men. IT was not associated with increased mortality in either sex. Appropriate shock therapy was a strong predictor of death in both, with women showing a 2-fold higher risk than men during post-shock long-term follow-up.

Abstract

Sustained growth in the arrhythmia population at Stanford Health Care led to an independent nurse practitioner-run outpatient direct current cardioversion (DCCV) program in 2012. DCCVs performed by a medical doctor, a nurse practitioner under supervision, or nurse practitioners from 2009 to 2014 were compared for safety and efficacy. A retrospective review of the electronic medical records system (Epic) was performed on biodemographic data, cardiovascular risk factors, medication history, procedural data, and DCCV outcomes. A total of 869 DCCVs were performed on 557 outpatients. Subjects were largely men with an average age of 65 years; 1/3 were obese; most had atrial fibrillation; and majority of subjects were on warfarin. The success rate of the DCCVs was 93.4% (812 of 869) with no differences among the groups. There were no short-term complications: stroke, myocardial infarction, or death. The length of stay was shortest in the NP group compared to the other groups (p <0.001). In conclusion, the success rate of DCCV in all groups was extremely high, and there were no complications in any of the DCCV groups.

Abstract

The cryoballoon catheter has proven to be both safe and effective when used for pulmonary vein (PV) isolation in patients with paroxysmal atrial fibrillation (AF). More recently, the cryoballoon catheter has demonstrated the ability to create durable, transmural, and large areas of PV ablation. However, persistent and long-standing persistent AF can require additional cardiac substrate modification(s) before a patient is returned to normal sinus rhythm. Yet, no study has reported the techniques necessary to achieve extra-PV lesion sets using the cryoballoon catheter.Cryoballoon ablation was completed in 225 patients with varying degrees of AF disease. In several cases, the balloon was used for more than PV isolation. This study examines the 11 anatomical cardiac locations where extra-PV lesion sets were utilized.This study demonstrates that these extra-PV ablations can be done safely with the balloon catheter (3.6 % total complication rate). The 12-month efficacy (freedom from all atrial arrhythmia) using these techniques was 88 % in 88 patients with paroxysmal AF, 71 % in 75 patients with persistent AF, and 55 % in 62 patients with long-standing persistent AF. While using this protocol, mean procedure time was 2.2?±?0.6 h, and average fluoroscopy time was 4.2?±?2.2 min.The cryoballoon catheter can be used to make effective and safe extra-PV lesions. However, these techniques will need to be validated in more multi-center studies with review of complication rates and long-term freedom from AF.

Abstract

Randomized trials of left atrial appendage (LAA) closure with the Watchman device have shown varying results, and its cost effectiveness compared with anticoagulation has not been evaluated using all available contemporary trial data.We used a Markov decision model to estimate lifetime quality-adjusted survival, costs, and cost effectiveness of LAA closure with Watchman, compared directly with warfarin and indirectly with dabigatran, using data from the long-term (mean 3.8 year) follow-up of Percutaneous Closure of the Left Atrial Appendage Versus Warfarin Therapy for Prevention of Stroke in Patients With Atrial Fibrillation (PROTECT AF) and Prospective Randomized Evaluation of the Watchman LAA Closure Device in Patients With Atrial Fibrillation (PREVAIL) randomized trials. Using data from PROTECT AF, the incremental cost-effectiveness ratios compared with warfarin and dabigatran were $20?486 and $23?422 per quality-adjusted life year, respectively. Using data from PREVAIL, LAA closure was dominated by warfarin and dabigatran, meaning that it was less effective (8.44, 8.54, and 8.59 quality-adjusted life years, respectively) and more costly. At a willingness-to-pay threshold of $50?000 per quality-adjusted life year, LAA closure was cost effective 90% and 9% of the time under PROTECT AF and PREVAIL assumptions, respectively. These results were sensitive to the rates of ischemic stroke and intracranial hemorrhage for LAA closure and medical anticoagulation.Using data from the PROTECT AF trial, LAA closure with the Watchman device was cost effective; using PREVAIL trial data, Watchman was more costly and less effective than warfarin and dabigatran. PROTECT AF enrolled more patients and has substantially longer follow-up time, allowing greater statistical certainty with the cost-effectiveness results. However, longer-term trial results and postmarketing surveillance of major adverse events will be vital to determining the value of the Watchman in clinical practice.

Abstract

Previous observations have reported that the number of pacing stimuli required to entrain a tachycardia varies on the basis of arrhythmia type and location, but a quantitative formulation of the number needed to entrain (NNE) that unifies these observations has not been characterized.We sought to investigate the relationship between the number of pacing stimulations, the tachycardia cycle length (TCL), the overdrive pacing cycle length (PCL), and the postpacing interval (PPI) to accurately estimate the timing of tachycardia entrainment.First, we detailed a mathematical derivation unifying electrophysiological parameters with empirical confirmation in 2 patients undergoing catheter ablation of typical atrial flutter. Second, we validated our formula in 44 patients who underwent various catheter ablation procedures. For accuracy, we corrected for rate-related changes in conduction velocity.We derived the equations NNE = |(PPI - TCL)/(TCL - PCL)| + 1 and Tachycardia advancement = (NNE - 1) × (TCL - PCL) - (PPI - TCL), which state that the NNE and the amount of tachycardia advancement on the first resetting stimulation are determined using regularly measured intracardiac parameters. In the retrospective cohort, the observed PPI - TCL highly correlated with the predicted PPI - TCL (mean difference 5.8 ms; r = 0.97; P < .001), calculated as PPI - TCL = (NNE - 1) × (TCL - PCL) - tachycardia advancement.The number of pacing stimulations required to entrain a reentrant tachycardia is predictable at any PCL after correcting for cycle length-dependent changes in conduction velocity. This relationship unifies established empirically derived diagnostic and mapping criteria for supraventricular tachycardia and ventricular tachycardia. This relationship may help elucidate when antitachycardia pacing episodes are ineffective or proarrhythmic and could potentially serve as a theoretical basis to customize antitachycardia pacing settings for improved safety and effectiveness.

Abstract

Studies suggest that women with ischemic heart disease are less likely to experience appropriate ICD therapies for ventricular arrhythmias (VT/VF). We evaluated the influence of sex on arrhythmic events or death in subjects enrolled in MADIT-CRT.Arrhythmic event rates, defined as VT/VF treated with defibrillator therapy or all-cause death, were determined among 1,790 subjects enrolled in MADIT-CRT with documented 3-year follow-up. Predictors of VT/VF/death were identified using multivariate analysis. Ninety-one (21%) women and 466 (35%) men experienced VT/VF/death over the follow-up period. The overall probability of VT/VF/death was significantly lower in women versus men (HR 0.62; P < 0.001). The probability of VT/VF/death was the lowest in women with ischemic heart disease (HR 0.51; P = 0.003). In ICD subjects, the 3-year risk of VT/VF was lower in ischemic women versus men (P = 0.021), and in nonischemic women versus men (P = 0.049). The probability of VT/VF/death was significantly lower in women (HR 0.52; P = 0.007) and men (HR 0.74; P = 0.018) with LBBB who received CRT-D. Appropriate shock therapy strongly correlated with increased risk of death during postshock follow-up in women (HR 5.18; P = 0.001) and men (HR 1.63; P = 0.033); interaction P value of 0.034.In this substudy of MADIT-CRT, sex, etiology of heart disease and type of device implanted significantly influenced subsequent risk for VT/VF or death. Women with ischemic heart disease and women with LBBB who received CRT-D had the lowest incidence of VT/VF or death when compared to men. Appropriate shock therapy was a strong predictor of death, particularly in women.

Abstract

Since the release of the second-generation cryoballoon (CB2; Arctic Front Advance(TM), Medtronic Inc) and its design modifications with improved cooling characteristics, the technique, dosing, and complication profile is significantly different from that of the first-generation cryoballoon. A comprehensive report of CB2 procedural recommendations has not been reported.The purpose of this study was to review the current best practices from a group of experienced centers to create a user's consensus guide for CB2 ablation.High-volume operators with a combined experience of more than 3000 CB2 cases were interviewed, and consensus for technical and procedural best practice was established.Comprehensive review of the CB2 ablation best practice guide will provide a detailed technique for achieving safer and more effective outcomes for CB2 atrial fibrillation ablation.

Abstract

Identification of silent atrial fibrillation (AF) could prevent stroke and other sequelae.Screening for AF using continuous ambulatory electrocardiographic (ECG) monitoring can detect silent AF in asymptomatic in patients with known risk factors.We performed a single-center prospective screening study using a wearable patch-based device that provides up to 2 weeks of continuous ambulatory ECG monitoring (iRhythm Technologies, Inc.). Inclusion criteria were age ?55 years and ?2 of the following risk factors: coronary disease, heart failure, hypertension, diabetes, sleep apnea. We excluded patients with prior AF, stroke, transient ischemic attack, implantable pacemaker or defibrillator, or with palpitations or syncope in the prior year.Out of 75 subjects (all male, age 69 ± 8.0 years; ejection fraction 57% ± 8.7%), AF was detected in 4 subjects (5.3%; AF burden 28% ± 48%). Atrial tachycardia (AT) was present in 67% (?4 beats), 44% (?8 beats), and 6.7% (?60 seconds) of subjects. The combined diagnostic yield of sustained AT/AF was 11%. In subjects without sustained AT/AF, 11 (16%) had ?30 supraventricular ectopic complexes per hour.Outpatient extended ECG screening for asymptomatic AF is feasible, with AF identified in 1 in 20 subjects and sustained AT/AF identified in 1 in 9 subjects, respectively. We also found a high prevalence of asymptomatic AT and frequent supraventricular ectopic complexes, which may be relevant to development of AF or stroke. If confirmed in a larger study, primary screening for AF could have a significant impact on public health.

Abstract

Previous studies on biventricular (BIV) pacing and cardiac resynchronization therapy-defibrillator (CRT-D) efficacy have used arbitrarily chosen BIV pacing percentages, and no study has employed implantable cardioverter defibrillator (ICD) patients as a control group.Using Kaplan-Meier plots, we estimated the threshold of BIV pacing percentage needed for CRT-D to be superior to ICD on the end-point of heart failure (HF) or death in 1219 left bundle branch block (LBBB) patients in the MADIT-CRT trial. Patients were censored at the time of crossover. In multivariable Cox analyses, no difference was seen in the risk of HF/death between ICD and CRT-D patients with BIV pacing ?90% [HR = 0.78 (0.47-1.30), P = 0.344], and with increasing BIV pacing the risk of HF/death was decreased [CRT-D BIV 91-96% vs. ICD: HR = 0.63 (0.42-0.94), P = 0.024 and CRT-D BIV ?97% vs. ICD: HR = 0.32 (0.23-0.44), P < 0.001]. The risk of death alone was reduced by 52% in CRT-D patients with BIV ?97% (HR = 0.48, P < 0.016), when compared with ICD patients. Within the CRT-D group, for every 1 percentage point increase in BIV pacing, the risk of HF/death and death alone significantly decreased by 6 and 10%, respectively. Increasing BIV pacing percentage was associated with significant reductions in left ventricular volume.In patients with LBBB, who were in sinus rhythm at enrolment, BIV pacing exceeding 90% was associated with a benefit of CRT-D in HF/death when compared with ICD patients. Furthermore, BIV pacing ?97% was associated with an even further reduction in HF/death, a significant 52% reduction in death alone, and increased reverse remodelling. Clinical trials.gov identifier: NCT00180271.

Abstract

A bioinspired microhairy sensor is developed to enable ultraconformability on nonflat surfaces and significant enhancement in the signal-to-noise ratio of the retrieved signals. The device shows ?12 times increase in the signal-to-noise ratio in the generated capacitive signals, allowing the ultraconformal microhair pressure sensors to be capable of measuring weak pulsations of internal jugular venous pulses stemming from a human neck.

Abstract

There are limited data regarding the effect of age on the risk of ventricular tachyarrhythmias (VTAs). The present study was designed to compare the risk for VTAs in young and older patients with left bundle branch block (LBBB) and mildly symptomatic heart failure who receive device therapy. The risk of the first ventricular tachycardia (VT) or ventricular fibrillation (VF) event and the risk of first appropriate implantable cardioverter defibrillator (ICD) shock was compared between young (<75 years, n = 1,037) and older (?75 years, n = 227) patients with LBBB enrolled in Multicenter Automatic Implantation Trial with Cardiac Resynchronization Therapy. The cumulative incidence of a first VTA through 2 years of follow-up was significantly lower in older patients than in younger patients. Multivariate analysis showed that older patients experienced a significantly lower risk of VT/VF (hazard ratio 0.38, 95% confidence interval 0.22 to 0.64, p <0.001) and a significantly lower risk of appropriate ICD shocks (hazard ratio 0.37, 95% confidence interval 0.17 to 0.82, p = 0.014) compared with younger patients. Each increasing decade of life was associated with a 19% (p = 0.002) and 22% (p = 0.018) reduction in the risk of VT/VF and appropriate ICD shocks, respectively. The lower risk of VT/VF and appropriate ICD shocks in older patients was evident in patients implanted with an ICD only and in those implanted with a cardiac resynchronization therapy with defibrillator. In conclusion, in patients with LBBB and mild symptoms of heart failure, aging is associated with a significant decrease in the incidence of VT/VF and ICD shocks.

Abstract

The preferential citation of studies with the highest success rates could exaggerate perceived effectiveness, particularly for treatments with widely varying published success rates such as radiofrequency catheter ablation for atrial fibrillation.We systematically identified observational studies and clinical trials of radiofrequency catheter ablation of atrial fibrillation between 1990 and 2012. Generalized Poisson regression was used to estimate association between study success rate and total citation count, adjusting for sample size, journal impact factor, time since publication, study design, and whether first or last author was a consensus-defined pre-eminent expert. We identified 174 articles meeting our inclusion criteria (36 289 subjects). After adjustment only for time since publication, a 10-point increase above the mean in pooled reported success rates was associated with a 17.8% increase in citation count at 5 years postpublication (95% confidence interval, 7.1-28.4%; P<0.001). After additional adjustment for impact factor, sample size, randomized trial design, and pre-eminent expert authorship, the association remained significant (18.6% increase in citation count; 95% confidence interval, 7.6-29.6%; P<0.0001). In this full model, time since publication, impact factor, and pre-eminent expert authorship were significant covariates, whereas randomized control trial design and study sample size were not.Among studies of radiofrequency catheter ablation of atrial fibrillation, high success rate was independently associated with citation count, which may indicate citation bias. To readers of the literature, radiofrequency catheter ablation of atrial fibrillation could be perceived to be more effective than the data supports. These findings may have implications for a wide variety of novel cardiovascular therapies.

Abstract

There are no prior studies assessing the relationship between left atrial volume (LAV) and inappropriate implantable cardioverter-defibrillator (ICD) therapy following treatment with cardiac resynchronization therapy.The purpose of this study was to investigate the hypothesis that patients randomized to cardiac resynchronization therapy with defibrillator (CRT-D) in the Multicenter Automatic Defibrillator Trial-Cardiac Resynchronization Therapy (MADIT-CRT) who had significant LAV reductions would have reduced risks of inappropriate ICD therapy.Cardiac resynchronization remodeling was assessed by measuring LAV change between baseline and 12-month echocardiograms in 751 CRT-D treated patients. Patients were stratified into quartiles based on percent reduction of LAV change. High LAV responders were those in the highest 3 quartiles of LAV reduction (LAV reduction ?21%). Low LAV responders were those in the lowest quartile of LAV reduction (LAV reduction <21%). Clinical factors associated with ?21% reduction in LAV were evaluated by linear regression analysis.In Cox proportional hazards regression analyses, high LAV responders had a 39% reduction in the risk of inappropriate therapy (hazard ratio 0.61, P = .04) and left bundle branch block patients exhibited an even greater risk reduction in inappropriate therapy (hazard ratio 0.51, P = .02) compared to low LAV responders during follow-up extending up to 3 years after the 12-month echocardiogram. High LAV responders also had a significantly lower risk of heart failure or death during follow-up than did low LAV responders.A ?21% reduction in LAV with cardiac resynchronization therapy is associated with significant reductions in inappropriate ICD therapy and in heart failure or death during a 3-year follow-up.

Abstract

The major risks of pacemaker and implantable cardioverter defibrillator extraction are attributable to the fibrotic tissue that encases them in situ, yet little is known about the cellular and functional properties of this response. In the present research, we performed a histological and mechanical analysis of human tissue collected from the lead-tissue interface to better understand this process and provide insights for the improvement of lead design and extraction. The lead-tissue interface consisted of a thin cellular layer underlying a smooth, acellular surface, followed by a circumferentially organized collagen-rich matrix. 51.8±4.9% of cells were myofibroblasts via immunohistochemistry, with these cells displaying a similar circumferential organization. Upon mechanical testing, samples exhibited a triphasic force-displacement response consisting of a toe region during initial tensioning, a linear elastic region and a yield and failure region. Mean fracture load was 5.6±2.1N, and mean circumferential stress at failure was 9.5±4.1MPa. While the low cellularity and fibrotic composition of tissue observed herein is consistent with a foreign body reaction to an implanted material, the significant myofibroblast response provides a mechanical explanation for the contractile forces complicating extractions. Moreover, the tensile properties of this tissue suggest the feasibility of circumferential mechanical tissue disruption, similar to balloon angioplasty devices, as a novel approach to assist with lead extraction.

Abstract

This study aimed to investigate the effect of both history of intermittent atrial tachyarrhythmias (IAT) and in-trial IAT on the risk of heart failure (HF) or death comparing cardiac resynchronization therapy with defibrillator (CRT-D) to implantable cardioverter-defibrillator (ICD) treatment in mildly symptomatic HF patients with left bundle branch block (LBBB).Limited data exist regarding the benefit of CRT-D in patients with IAT.The benefit of CRT-D in reducing the risk of HF/death was evaluated using multivariate Cox models incorporating the presence of, respectively, a history of IAT at baseline and time-dependent development of in-trial IAT during follow-up in 1,264 patients with LBBB enrolled in the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy) study.The overall beneficial effect of CRT-D versus ICD on the risk of HF/death was not significantly different between LBBB patients with or without history of IAT (HR: 0.50, p = 0.028, and HR: 0.46, p < 0.001, respectively; p for interaction = 0.79). Among patients who had in-trial IAT, CRT-D was associated with a significant 57% reduction in the risk of HF/death compared with ICD-only therapy (HR: 0.43, p = 0.047), similar to the effect of the device among patients who did not have IAT (HR: 0.47, p < 0.001; p for interaction = 0.85). The percentage of patients with biventricular pacing ?92% was similar in both groups (p = 0.43). Consistent results were shown for the benefit of CRT-D among patients who had in-trial atrial fibrillation/flutter (HR: 0.30, p = 0.027; p for interaction = 0.41).In the MADIT-CRT study, the clinical benefit of CRT-D in LBBB patients was not attenuated by prior history of IAT or by the development of in-trial atrial tachyarrhythmias. (MADIT-CRT: Multicenter Automatic Defibrillator Implantation Trial With Cardiac Resynchronization Therapy; NCT00180271).

Abstract

Atrial fibrillation (AF) is the most common arrhythmia among patients with hypertrophic cardiomyopathy (HCM). The relationship between paroxysmal AF and exercise capacity in this population is incompletely understood.Patients with HCM underwent symptom-limited cardiopulmonary testing with expired gas analysis at Stanford Hospital between October 2006 and October 2012. Baseline demographics, medical histories and resting echocardiograms were obtained for all subjects. Diagnosis of AF was established by review of medical records and baseline ECG. Those with paroxysmal AF were in sinus rhythm at the time of cardiopulmonary testing with expired gas analysis. Exercise intolerance was defined as peak VO2<20 mL/kg/min. We used multivariate logistic regression to evaluate the association between exercise intolerance and paroxysmal AF.Among the 265 patients recruited, 55 had AF (28 paroxysmal and 27 permanent). Compared with those without AF, subjects with paroxysmal AF were older, more likely to use antiarrhythmic and anticoagulant medications, and had larger left atria. Patients with paroxysmal AF achieved lower peak VO2 (21.9±9.2 mL/kg/min vs 26.9±10.8 mL/kg/min, p=0.02) and were more likely to have exercise intolerance (61% vs 28%, p<0.001) compared with those without AF. After adjustment for age, sex and body mass index (BMI) exercise intolerance remained significantly associated with paroxysmal AF (OR 4.65, 95% CI 1.83 to 11.83, p=0.001).Patients with HCM and paroxysmal AF demonstrate exercise intolerance despite being in sinus rhythm at the time of exercise testing.

Abstract

With increasing complexity in electrophysiology (EP) procedures, the use of electroanatomic mapping systems (EAMS) as a supplement to fluoroscopy has become common practice. This is the first study that evaluates spatial and point localization accuracy for 2 current EAMS, CARTO3(®) (Biosense Webster, Diamond Bar, CA, USA) and EnSite Velocity(®) (St. Jude Medical Inc., St. Paul, MN, USA), and for a novel overlay guidance (OG) software (Siemens AG, Forchheim, Germany) in a phantom experiment.A C-arm CT scan was performed on an acrylic phantom containing holes and location markers. Spatial accuracy was assessed for each system using distance measurements involving known markers inside the phantom and properly placed catheters. Anatomical maps of the phantom were acquired by each EAMS, whereas the 3D-based OG software superimposed an overlay image of the phantom, segmented from the C-arm CT data set, onto biplane fluoroscopy. Registration processes and landmark measurements quantitatively assessed the spatial accuracy of each technology with respect to the ground truth phantom. Point localization performance was 0.49 ± 0.25 mm in OG, 0.46 ± 0.17 mm in CARTO3(®) and 0.79 ± 0.83 mm in EnSite(®) . The registration offset between virtual visualization and reality was 1.10 ± 0.52 mm in OG, 1.62 ± 0.77 mm in CARTO3(®) and 2.02 ± 1.21 mm in EnSite(®) . The offset to phantom C-arm CT landmark measurements was 0.30 ± 0.26 mm in OG, 0.24 ± 0.21 mm in CARTO3(®) and 1.32 ± 0.98 mm in EnSite(®) .Each of the evaluated EP guidance systems showed a high level of accuracy; the observed offsets between the virtual 3D visualization and the real phantom were below a clinically relevant threshold of 3 mm.

Abstract

Sudden cardiac death is a well-documented public health problem and the implantable cardioverter defibrillator (ICD) has demonstrated benefit in reducing mortality. Prospective patients must identify and evaluate the ICD's pros and cons and produce a personal decision. The purpose of this study was to create and evaluate a measure of patient-evaluated pros and cons of the ICD, and its relationship to patient decision regarding ICD implantation.The ICD-decision analysis scale (ICD-DAS) was created and tested in prospective ICD recipients (N = 104). Factor analysis was performed to evaluate interitem relationships, and subsequently, identified subscales; additional psychosocial measures were used to predict the ICD decision. A two-factor measure for ICD decision making was established with two subscales: ICD Pros and ICD Cons. The subscales have high internal consistency and were strong predictors of intent to choose an ICD. Other psychosocial measures were not significantly predictive of ICD Choice, yet simultaneous entry of ICD Pros and Cons subscales resulted in a significant increase in R(2) , F(2, 59) = 19.36, P < 0.001. The full model was significantly greater than zero, F(11, 70) = 5.017, P < 0.001, R(2) = 0.48.The ICD-DAS provides the first empirically tested and clinically useful approach to understanding the specific pros and cons for prospective ICD patients. The measure can assist clinicians with patient-centered discussions regarding sudden cardiac arrest treatments. The ICD-DAS will allow for the provision of tailored education or counseling and may be used to predict postdecision outcomes.

Abstract

Intravenous amiodarone is an important treatment for arrhythmias, but peripheral infusion is associated with direct irritation of vessel walls and phlebitis rates of 8% to 55%. Objectives To determine the incidence and factors contributing to the development of amiodarone-induced phlebitis in the coronary care unit in an academic medical center and to refine the current practice protocol.Medical records from all adult patients during an 18-month period who received intravenous amiodarone while in the critical care unit were reviewed retrospectively. Route of administration, location, concentration, and duration of amiodarone therapy and factors associated with occurrence of phlebitis were examined. Descriptive statistics and regression methods were used to identify incidence and phlebitis factors.In the final sample of 105 patients, incidence of phlebitis was 40%, with a 50% recurrence rate. All cases of phlebitis occurred in patients given a total dose of 3 g via a peripheral catheter, and one-quarter of these cases (n = 10) developed at dosages less than 1 g. Pain, redness, and warmth were the most common indications of phlebitis. Total dosage given via a peripheral catheter, duration of infusion, and number of catheters were significantly associated with phlebitis.Amiodarone-induced phlebitis occurred in 40% of this sample at higher drug dosages. A new practice protocol resulted from this study. An outcome study is in progress.

Abstract

The Stanford Biodesign Program began in 2001 with a mission of helping to train leaders in biomedical technology innovation. A key feature of the program is a full-time postgraduate fellowship where multidisciplinary teams undergo a process of sourcing clinical needs, inventing solutions and planning for implementation of a business strategy. The program places a priority on needs identification, a formal process of selecting, researching and characterizing needs before beginning the process of inventing. Fellows and students from the program have gone on to careers that emphasize technology innovation across industry and academia. Biodesign trainees have started 26 companies within the program that have raised over $200 million and led to the creation of over 500 new jobs. More importantly, although most of these technologies are still at a very early stage, several projects have received regulatory approval and so far more than 150,000 patients have been treated by technologies invented by our trainees. This paper reviews the initial outcomes of the program and discusses lessons learned and future directions in terms of training priorities.

Abstract

Cardiotoxicity is a leading cause for drug attrition during pharmaceutical development and has resulted in numerous preventable patient deaths. Incidents of adverse cardiac drug reactions are more common in patients with preexisting heart disease than the general population. Here we generated a library of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from patients with various hereditary cardiac disorders to model differences in cardiac drug toxicity susceptibility for patients of different genetic backgrounds.Action potential duration and drug-induced arrhythmia were measured at the single cell level in hiPSC-CMs derived from healthy subjects and patients with hereditary long QT syndrome, familial hypertrophic cardiomyopathy, and familial dilated cardiomyopathy. Disease phenotypes were verified in long QT syndrome, hypertrophic cardiomyopathy, and dilated cardiomyopathy hiPSC-CMs by immunostaining and single cell patch clamp. Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) and the human ether-a-go-go-related gene expressing human embryonic kidney cells were used as controls. Single cell PCR confirmed expression of all cardiac ion channels in patient-specific hiPSC-CMs as well as hESC-CMs, but not in human embryonic kidney cells. Disease-specific hiPSC-CMs demonstrated increased susceptibility to known cardiotoxic drugs as measured by action potential duration and quantification of drug-induced arrhythmias such as early afterdepolarizations and delayed afterdepolarizations.We have recapitulated drug-induced cardiotoxicity profiles for healthy subjects, long QT syndrome, hypertrophic cardiomyopathy, and dilated cardiomyopathy patients at the single cell level for the first time. Our data indicate that healthy and diseased individuals exhibit different susceptibilities to cardiotoxic drugs and that use of disease-specific hiPSC-CMs may predict adverse drug responses more accurately than the standard human ether-a-go-go-related gene test or healthy control hiPSC-CM/hESC-CM screening assays.

Abstract

The aim of our study was to evaluate the relationship between left ventricular (LV) dyssynchrony and the risk of ventricular tachycardia (VT) or ventricular fibrillation (VF) in patients enrolled in the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy) trial.Intraventricular mechanical dyssynchrony might be an important factor in ventricular arrhythmogenesis by enhancing electrical heterogeneity in heart failure patients. The effects of dyssynchrony have not yet been evaluated in a large cohort of implantable cardioverter-defibrillator (ICD) and cardiac resynchronization therapy with defibrillator (CRT-D) patients.LV dyssynchrony was measured at baseline and at 12-months by speckle-tracking echocardiography, defined as the standard deviation of time to peak systolic strain in 12 LV myocardial segments. The endpoint was the first VT/VF/death or VT/VF. LV dyssynchrony was evaluated in 764 left bundle branch block (LBBB) patients and in 312 non-LBBB patients.Baseline LV dyssynchrony was not predictive of VT/VF/death or VT/VF in LBBB or non-LBBB patients in either treatment arm. In CRT-D patients with LBBB, improvement in LV dyssynchrony over a year was associated with significantly lower incidence of VT/VF/death (p < 0.001) and VT/VF (p < 0.001) compared to ICD patients and to CRT-D patients with unchanged or worsening dyssynchrony. Among LBBB patients, 15% decrease in LV dyssynchrony was associated with lower risk of VT/VF/death (hazard ratio: 0.49, 95% confidence interval: 0.24 to 0.99, p = 0.049) and VT/VF (hazard ratio: 0.30, 95% confidence interval: 0.12 to 0.77, p = 0.009) as compared to ICD patients. Patients without LBBB receiving CRT-D did not show reduction in VT/VF/death or in VT/VF in relation to improving dyssynchrony when evaluating cumulative event rates or risk of events.Baseline LV dyssynchrony did not predict VT/VF/death or VT/VF in mild heart failure patients with or without LBBB. CRT-induced improvement of LV dyssynchrony was associated with significant reduction of ventricular arrhythmias in patients with LBBB.

Abstract

We aimed to evaluate the influence of left ventricular (LV) lead position on the risk of ventricular tachyarrhythmias in cardiac resynchronization therapy (CRT) patients.Left ventricular (LV) lead position was evaluated by biplane coronary venograms and anterior/posterior, lateral chest X-rays in patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial - Cardiac Resynchronization Therapy (MADIT-CRT). The LV lead location could be defined in 797 of 1089 patients (73%). The LV lead was placed at the LV apex in 110 (14%) patients, in the anterior position in 146 (18%), in the lateral position in 448 (56%), and in the posterior position in 93 (12%) patients. After adjustment for clinical covariates, lateral or posterior lead location was associated with significantly lower risk of ventricular tachycardia (VT)/ventricular fibrillation (VF) [hazard ratio (HR) = 0.57, 95% confidence interval (CI): 0.38-0.85; P = 0.006] when compared with an anterior lead location. Patients with anterior lead position had similar risk of VT/VF as patients with implantable cardioverter defibrillator (ICD)-only (HR = 1.04, 95% CI: 0.72-1.81; P = 0.837). There was no difference in the risk of mortality between posterior or lateral and anterior LV lead locations.Cardiac resynchronization therapy with posterior or lateral LV lead position is associated with decreased risk of arrhythmic events in comparison with anterior lead location and ICD-only patients. There is no evidence for increased risk of VT/VF episodes associated with CRT.

Abstract

Atrial fibrillation (AF) is less prevalent in women versus men, but associated with higher risks of stroke and death in women. The role hormone therapy plays in AF is not well understood.The Women's Health Initiative randomized postmenopausal women to placebo or conjugated equine estrogens (0.625 mg/d) plus medroxyprogesterone acetate (2.5 mg/d) if they had a uterus (N=16 608) or to conjugated equine estrogens only if they had prior hysterectomy (N=10 739). Incident AF was identified by ECG and diagnosis codes from Medicare claims or hospitalization records. Hazard ratios for incident AF were estimated using Cox proportional hazards regression. After excluding participants with baseline AF, there were 611 incident AF cases over a mean of 5.6 years among 16 128 estrogen plus progestin participants, and 683 cases over a mean of 7.1 years among 10 251 conjugated equine estrogens alone participants. Incident AF was more frequent in the active groups of both trials, reaching statistical significance in the trial of conjugated equine estrogens alone in women with prior hysterectomy (hazard ratio, 1.17; CI, 1.00-1.36; P=0.045) and in the pooled analysis (hazard ratio, 1.12; CI, 1.00-1.24; P=0.05), but not in the estrogen plus progestin trial (hazard ratio, 1.07; CI, 0.91-1.25; P=0.44). These results were only minimally affected by adjustment for incident stroke, coronary heart disease, and heart failure.Incident AF was modestly elevated in hysterectomized women randomized to postmenopausal E-alone, and in the pooled group randomized to E-alone or estrogen plus progestin. The trend in women with intact uterus receiving estrogen plus progestin, considered separately, was not statistically significant.ClinicalTrials.gov; Identifier: NCT00000611.

Abstract

This study hypothesized that time-dependent statin therapy will reduce the risk of life-threatening ventricular tachyarrhythmias among patients with nonischemic cardiomyopathy (NICM) enrolled in the MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy).Prior studies suggested that statin therapy exerts antiarrhythmic properties among patients with coronary artery disease. However, data regarding the effect of statins on arrhythmic risk among patients with NICM are limited.Multivariate Cox proportional hazards regression modeling was used to assess the effect of statin therapy, evaluated as a time-dependent covariate, on the risk of appropriate defibrillator therapy for fast ventricular tachycardia (VT) (defined as a rate faster than 180 beats/min)/ventricular fibrillation (VF) or death (primary endpoint) and appropriate defibrillator shocks (secondary endpoint) among 821 patients with NICM enrolled in the MADIT-CRT trial.Statin users (n = 499) were older and had a higher prevalence of diabetes and hypertension yet were less frequently smokers. Multivariate analysis showed that time-dependent statin therapy was independently associated with a significant 77% reduction in the risk of fast VT/VF or death (p < 0.001) and with a significant 46% reduction in the risk of appropriate implantable cardioverter defibrillator shocks (p = 0.01). Consistent with these findings, the cumulative probability of fast VT/VF or death at 4 years of follow-up was significantly lower among patients who were treated with statins (11%) as compared with study patients who were not treated with statins (19%; p = 0.006 for the overall difference during follow-up).Statin use was associated with a significant reduction in the risk of life-threatening ventricular tachyarrhythmias among patients with NICM.

Abstract

Determination of the defibrillation safety margin (DSM) is the most common method of testing device effectiveness at the time of implantation of implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy defibrillator (CRTD). Low DSM remains a problem in clinical practice.The purpose of this study is to ascertain the incidence and clinical predictors of low DSM and the treatment strategies for low DSM in ICD or CRTD recipients.Selected ICD or CRTD recipients from January 2006 to May 2008 who underwent DSM test at the time of implantation were included. Low DSM patients were defined as patients who had a DSM within 10 J of the maximum delivered energy of the device. These patients were compared to patients who had DSM?>?10 J.This study included 243 patients. Of these, 13 (5.3%) patients had low DSM, and 230 patients had adequate DSM. Patients with low DSM had a high prevalence of amiodarone use (69% vs 13%, p?0.01), secondary prevention indications (69% vs 30%, p?0.01), and a trend toward younger age (51?±?18 vs 58?±?15 years, p?=?0.08). After adjustment for age and sex, amiodarone use was significantly associated with low DSM. All low DSM patients except one obtained adequate DSM after taking additional steps, including discontinuing amiodarone and starting sotalol, RV lead repositioning, adding a subcutaneous array or shock coil, changing single-coil to dual-coil lead, and upgrading to a high output device.The incidence of low DSM patients is low with high-energy devices. Amiodarone use is associated with low DSM, and its discontinuation or substitution with sotalol is one of a variety of available options for low DSM patients.

Abstract

Prior studies have indicated that the magnitude of risk association of microvolt T-wave alternans (MTWA) testing appears to vary with the population studied. We performed a meta-analysis to determine the ability of MTWA to modify risk assessment of ventricular tachyarrhythmic events (VTEs) and sudden cardiac death (SCD) across a series of patient risk profiles using likelihood ratio (LR) testing, a measure of test performance independent of disease prevalence.We identified original research articles published from January 1990 to January 2011 that investigate spectrally derived MTWA. Ventricular tachyarrhythmic event was defined as the total and arrhythmic mortality and nonfatal sustained or implantable cardioverter-defibrillator-treated ventricular tachyarrhythmias. Summary estimates were created for positive and nonnegative MTWA results using a random-effects model and were expressed as positive (LR+) and negative (LR-) LRs.Of 1,534 articles, 20 prospective cohort studies met our inclusion criteria, consisting of 5,945 subjects predominantly with prior myocardial infarction or left ventricular dysfunction. Although there was a modest association between positive MTWA and VTE (relative risk 2.45, 1.58-3.79) and nonnegative MTWA and VTE (3.68, 2.23-6.07), test performance was poor (positive MTWA: LR+ 1.78, LR- 0.43; nonnegative MTWA: LR+ 1.38, LR- 0.56). Subgroup analyses of subjects classified as prior VTE, post-myocardial infarction, SCD-HeFT type, and MADIT-II type had a similar poor test performance. A negative MTWA result would decrease the annualized risk of VTE from 8.85% to 6.37% in MADIT-II-type patients and from 5.91% to 2.60% in SCD-HeFT-type patients.Despite a modest association, results of spectrally derived MTWA testing do not sufficiently modify the risk of VTE to change clinical decisions.

Abstract

The impact of atrial fibrillation on the healthcare systems of Western countries is overwhelming, due to its independent association with death, systemic thromboembolism, impaired quality of life and hospitalizations. Catheter ablation is the only treatment thus far demonstrated capable of achieving cure in a substantial proportion of patients. Pulmonary vein antrum isolation (PVAI) is the cornerstone of current atrial fibrillation ablation techniques, with the greatest efficacy as a stand-alone procedure in patients with paroxysmal atrial fibrillation. Use of general anesthesia, open-irrigated ablation catheters and maintenance of periprocedural therapeutic warfarin has been demonstrated to increase the safety and effectiveness of PVAI. In patients with paroxysmal atrial fibrillation, the systematic addition of superior vena cava isolation increases the long-term freedom from atrial fibrillation recurrence. A more extensive ablation approach extending to the entire left atrial posterior wall and to complex fractionated electrograms (CFAEs) is warranted in nonparoxysmal atrial fibrillation patients, in whom nonpulmonary vein trigger sites are frequently identified. Up to one-third of these patients experiencing atrial fibrillation recurrence after ablation have evidence of triggers from the left atrial appendage. Isolation of this structure is the best treatment strategy to improve the long-term success rate. In recent years, in addition to the development of ablation techniques to increase the success rate, outcomes of atrial fibrillation treatment trials have been reconsidered. In particular, reduction of hospitalization, stroke and mortality, as well as economic factors, have all been considered relevant to evaluate the effectiveness of atrial fibrillation treatment. Large ongoing trials are specifically evaluating the impact of atrial fibrillation ablation on these outcomes. This article will summarize the state-of-the art techniques for atrial fibrillation ablation, and will discuss the contribution of ongoing studies to the future of atrial fibrillation ablation.

Abstract

The purpose of this study was to estimate rates and identify predictors of inpatient complications and 30-day readmissions, as well as repeat hospitalization rates for arrhythmia recurrence following atrial fibrillation (AF) ablation.AF is the most common clinically significant arrhythmia and is associated with increased morbidity and mortality. Radiofrequency or cryotherapy ablation of AF is a relatively new treatment option, and data on post-procedural outcomes in large general populations are limited.Using data from the California State Inpatient Database, we identified all adult patients who underwent their first AF ablation from 2005 to 2008. We used multivariable logistic regression to identify predictors of complications and/or 30-day readmissions and Kaplan-Meier analyses to estimate rates of all-cause and arrhythmia readmissions.Among 4,156 patients who underwent an initial AF ablation, 5% had periprocedural complications, most commonly vascular, and 9% were readmitted within 30 days. Older age, female, prior AF hospitalizations, and less hospital experience with AF ablation were associated with higher adjusted risk of complications and/or 30-day readmissions. The rate of all-cause hospitalization was 38.5% by 1 year. The rate of readmission for recurrent AF, atrial flutter, and/or repeat ablation was 21.7% by 1 year and 29.6% by 2 years.Periprocedural complications occurred in 1 of 20 patients undergoing AF ablation, and all-cause and arrhythmia-related rehospitalizations were common. Older age, female sex, prior AF hospitalizations, and recent hospital procedure experience were associated with a higher risk of complications and/or 30-day readmission after AF ablation.

Abstract

We hypothesized that reductions in left atrial volume (LAV) with a cardiac resynchronization therapy-defibrillator (CRT-D) would translate into a subsequent reduction in the risk of atrial tachyarrhythmias (AT).There is limited information regarding the effect of CRT-D on the risk of AT.Percent reduction in LAV at 1 year following CRT-D implantation (pre-specified as low [lowest quartile: <20% reduction in LAV] and high [?20% reduction in LAV] response to CRT-D) were related to the risk of subsequent AT (comprising atrial fibrillation, atrial flutter, atrial tachycardia, and supraventricular tachyarrhythmias) among patients enrolled in MADIT-CRT (Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy).The cumulative probability of AT 2.5 years after assessment of echocardiographic response was lowest among high LAV responders to CRT-D (3%) and significantly higher among both low LAV responders to CRT-D (9%) and implantable cardioverter-defibrillator-only patients (7%; p = 0.03 for the difference among the 3 groups). Consistently, multivariate analysis showed that high LAV responders to CRT-D experienced a significant 53% (p = 0.01) reduction in the risk of subsequent AT as compared with implantable cardioverter-defibrillator-only patients, whereas low LAV responders did not derive a significant risk reduction with CRT-D therapy (hazard ratio [HR]: 1.05 [95% confidence interval (CI): 0.54 to 2.00]; p = 0.89). Patients who developed in-trial AT experienced significant increases in the risk for both the combined endpoint of heart failure or death (HR: 2.28 [95% CI: 1.45 to 3.59]; p < 0.001) and the separate occurrence of all-cause mortality (HR: 1.89 [95% CI: 1.08 to 3.62]; p = 0.01).In the MADIT-CRT study, favorable reverse remodeling of the left atrium with CRT-D therapy was associated with a significant reduction in risk of subsequent AT. (Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy [MADIT-CRT]; NCT00180271).

Abstract

During radiofrequency catheter ablation for atrial fibrillation, the esophagus is at risk for thermal injury. In this study, C-arm computed tomography (CT) was compared to clinical CT, without the administration of oral contrast, to visualize the esophagus and its relationship to the left atrium and the ostia of the pulmonary veins (PVs) during the radiofrequency ablation procedure.Sixteen subjects underwent both cardiac clinical CT and C-arm CT. Computed tomographic scans were performed on a multidetector scanner using a standard electrocardiographically gated protocol. C-arm computed tomographic scans were obtained using either a multisweep protocol with retrospective electrocardiographic gating or a non-gated single-sweep protocol. C-arm and clinical computed tomographic scans were analyzed in a random order and then compared for the following criteria: (1) visualization of the esophagus (yes or no), (2) relationship of esophageal position to the four PVs, and (3) direct contact or absence of a fat pad between the esophagus and the PV antrum.The esophagus was identified in all C-arm and clinical computed tomographic scans. In four cases, orthogonal planes were needed on C-arm CT (inferior PV level). In six patients, the esophageal location on C-arm CT was different from that on CT. Direct contact was reported in 19 of 64 of the segments (30%) examined on CT and in 26 of 64 (41%) on C-arm CT. In five of 64 segments (8%), C-arm CT overestimated a direct contact of the esophagus to the left atrium.C-arm computed tomographic image quality without the administration of oral contrast agents was shown to be sufficient for visualization of the esophagus location during a radiofrequency catheter ablation procedure for atrial fibrillation.

Abstract

The advent of subcutaneous implantable cardioverter-defibrillator (ICD) systems represents a paradigm shift for the detection and therapy of ventricular tachyarrhythmias. Despite advances in transvenous lead technology, problems remain that notably include requirement for technical expertise; periprocedural complications during implantation and explantation; and long-term lead failure. Although subcutaneous ICD systems may mitigate some of these risks, they provide new shortcomings, such as inability to provide pacing therapy for bradyarrhythmias, ventricular tachyarrhythmias, and cardiac resynchronization. Ongoing clinical evaluation and development are required before the role of subcutaneous ICDs as an adjunctive or primary therapy can be defined. This article examines studies investigating the subcutaneous ICD and discusses its possible advantages and disadvantages as compared with current transvenous ICD systems.

Abstract

This study aimed to determine whether QRS morphology identifies patients who benefit from cardiac resynchronization therapy with a defibrillator (CRT-D) and whether it influences the risk of primary and secondary end points in patients enrolled in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT) trial.Baseline 12-lead ECGs were evaluated with regard to QRS morphology. Heart failure event or death was the primary end point of the trial. Death, heart failure event, ventricular tachycardia, and ventricular fibrillation were secondary end points. Among 1817 patients with available sinus rhythm ECGs at baseline, there were 1281 (70%) with left bundle-branch block (LBBB), 228 (13%) with right bundle-branch block, and 308 (17%) with nonspecific intraventricular conduction disturbances. The latter 2 groups were defined as non-LBBB groups. Hazard ratios for the primary end point for comparisons of CRT-D patients versus patients who only received an implantable cardioverter defibrillator (ICD) were significantly (P < 0.001) lower in LBBB patients (0.47; P < 0.001) than in non-LBBB patients (1.24; P = 0.257). The risk of ventricular tachycardia, ventricular fibrillation, or death was decreased significantly in CRT-D patients with LBBB but not in non-LBBB patients. Echocardiographic parameters showed significantly (P < 0.001) greater reduction in left ventricular volumes and increase in ejection fraction with CRT-D in LBBB than in non-LBBB patients.Heart failure patients with New York Heart Association class I or II and ejection fraction ? 30% and LBBB derive substantial clinical benefit from CRT-D: a reduction in heart failure progression and a reduction in the risk of ventricular tachyarrhythmias. No clinical benefit was observed in patients with a non-LBBB QRS pattern (right bundle-branch block or intraventricular conduction disturbances).URL: http://www.clinicaltrials.gov. Unique identifier: NCT00180271.

Abstract

Warfarin reduces the risk for ischemic stroke in patients with atrial fibrillation (AF) but increases the risk for hemorrhage. Dabigatran is a fixed-dose, oral direct thrombin inhibitor with similar or reduced rates of ischemic stroke and intracranial hemorrhage in patients with AF compared with those of warfarin.To estimate the quality-adjusted survival, costs, and cost-effectiveness of dabigatran compared with adjusted-dose warfarin for preventing ischemic stroke in patients 65 years or older with nonvalvular AF.Markov decision model.The RE-LY (Randomized Evaluation of Long-Term Anticoagulation Therapy) trial and other published studies of anticoagulation. The cost of dabigatran was estimated on the basis of pricing in the United Kingdom.Patients aged 65 years or older with nonvalvular AF and risk factors for stroke (CHADS? score ?1 or equivalent) and no contraindications to anticoagulation.Lifetime.Societal.Warfarin anticoagulation (target international normalized ratio, 2.0 to 3.0); dabigatran, 110 mg twice daily (low dose); and dabigatran, 150 mg twice daily (high dose).Quality-adjusted life-years (QALYs), costs (in 2008 U.S. dollars), and incremental cost-effectiveness ratios.The quality-adjusted life expectancy was 10.28 QALYs with warfarin, 10.70 QALYs with low-dose dabigatran, and 10.84 QALYs with high-dose dabigatran. Total costs were $143 193 for warfarin, $164 576 for low-dose dabigatran, and $168 398 for high-dose dabigatran. The incremental cost-effectiveness ratios compared with warfarin were $51 229 per QALY for low-dose dabigatran and $45 372 per QALY for high-dose dabigatran.The model was sensitive to the cost of dabigatran but was relatively insensitive to other model inputs. The incremental cost-effectiveness ratio increased to $50 000 per QALY at a cost of $13.70 per day for high-dose dabigatran but remained less than $85 000 per QALY over the full range of model inputs evaluated. The cost-effectiveness of high-dose dabigatran improved with increasing risk for stroke and intracranial hemorrhage.Event rates were largely derived from a single randomized clinical trial and extrapolated to a 35-year time frame from clinical trials with approximately 2-year follow-up.In patients aged 65 years or older with nonvalvular AF at increased risk for stroke (CHADS? score ?1 or equivalent), dabigatran may be a cost-effective alternative to warfarin depending on pricing in the United States.American Heart Association and Veterans Affairs Health Services Research & Development Service.

Abstract

Family members of patients with established long-QT syndrome (LQTS) often lack definitive clinical findings, yet may have inherited an LQTS mutation and be at risk of sudden death. Genetic testing can identify mutations in 75% of patients with LQTS, but genetic testing of family members remains controversial.We used a Markov model to assess the cost-effectiveness of 3 strategies for treating an asymptomatic 10-year-old, first-degree relative of a patient with clinically evident LQTS. In the genetic testing strategy, relatives undergo genetic testing only for the mutation identified in the index patient, and relatives who test positive for the mutation are treated with ?-blockers. This strategy was compared with (1) empirical treatment of relatives with ?-blockers and (2) watchful waiting, with treatment only after development of symptoms. The genetic testing strategy resulted in better survival and quality-adjusted life years at higher cost, with a cost-effectiveness ratio of $67 400 per quality-adjusted life year gained compared with watchful waiting. The cost-effectiveness of the genetic testing strategy improved to less than $50 000 per quality-adjusted life year gained when applied selectively either to (1) relatives with higher clinical suspicion of LQTS (pretest probability 65% to 81%), or to (2) families with a higher than average risk of sudden death, or to (3) larger families (2 or more first-degree relatives tested).Genetic testing of young first-degree relatives of patients with definite LQTS is moderately expensive, but can reach acceptable thresholds of cost-effectiveness when applied to selected patients.

Abstract

Cardiac repolarization adaptation to cycle length change is patient dependent and results in complex QT-RR hysteresis. We hypothesize that accurate patient-specific QT-RR curves and rate corrected QT values (QTc) can be derived through patient-specific modeling of hysteresis.Model development was supported by QT-RR observations from 1959 treadmill tests, allowing extensive exploration of the influences of autonomic function on QT adaptation to rate changes. The methodology quantifies and then removes patient-specific repolarization adaptation rates. The estimated average 95% QT confidence limit was approximately 1 msec for the studied population. The model was validated by comparing QT-RR curves derived from a submaximal exercise protocol with rapid exercise and recovery phases, characterized by high hysteresis, with QT-RR values derived from an incremental stepped protocol that held heart rate constant for 5 minutes at each stage of exercise and recovery.The underlying physiologic changes affecting QT dynamics during the transitions from rest to exercise to recovery are quite complex. Nevertheless, a simple patient-specific model, comprising only three parameters and based solely on the preceding history of RR intervals and trend, is sufficient to accurately model QT hysteresis over an entire exercise test for a diverse population. A brief recording of a resting ECG, combined with a short period of submaximal exercise and recovery, provides sufficient information to derive an accurate patient-specific QT-RR curve, eliminating QTc bias inherent in population-based correction formulas.

Abstract

Coronary revascularization (CR) may confer electrical stability in patients with ischemic cardiomyopathy. However, data regarding the effect of CR on the development of ventricular tachyarrhythmias in this population are limited.The purpose of this study was to evaluate the association between CR and arrhythmic risk in postmyocardial infarction (post-MI) patients with left ventricular dysfunction.The risk for life-threatening ventricular tachyarrhythmias (defined as a first appropriate defibrillator therapy for ventricular tachycardia [VT]/ventricular fibrillation [VF] or death) was compared between post-MI patients with and those without prior CR (n = 612 and 147, respectively) enrolled in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT).The 3-year cumulative rate of VT/VF or death was significantly higher among patients without prior CR (42%) than in patients who underwent prior CR (32%, P = .02). Multivariate analysis demonstrated that patients without prior CR had 48% increased risk (P = .01) for VT/VF or death. Risk reduction associated with CR was related to elapsed time from CR, assessed both as a categorical variable (tertiles for time from CR: ?7 years, hazard ratio [HR] = 1.93, P = .001; 1.5-7 years, HR = 1.70, P = .01 vs <1.5 years) and as a continuous measure (4%, P = .002, increased risk for VT/VF or death per 1-year increment of elapsed time from CR). The effect of CR on arrhythmic risk was similar in patients treated with a defibrillator alone or when combined with cardiac resynchronization therapy.Post-MI patients with left ventricular dysfunction who undergo CR experience a time-dependent reduction in the risk for subsequent life-threatening ventricular tachyarrhythmias.

Abstract

A case of inappropriate atrial pacing in a patient with a pacemaker programmed with Managed Ventricular Pacing (MVP) mode, a proprietary algorithm in Medtronic devices, is presented. The patient was an 84-year-old woman who presented in sinus rhythm with complete atrioventricular block. A dual-chamber pacemaker was implanted and programmed to an MVP pacing mode. After the implant, the patient developed a relatively slow atrial tachyarrhythmia with 2:1 atrioventricular block and inappropriate atrial pacing, followed by a delay in tracking of the atrial tachyarrhythmia. The mechanisms for these behaviors are described.

Abstract

The CAPTURE study evaluated the accuracy of automated atrial and right ventricular (RV) threshold algorithms.Modern pacemakers include many added features designed to improve the ease of patient follow-up, as well as algorithms to reduce pacing outputs and/or reduce the atrial or ventricular pacing percentages, thus improving longevity.Automated atrial and RV threshold measurements were assessed versus manual measurements at 6 months. The projected longevity was assessed and compared between subjects with the threshold-tracking feature On versus Off. In addition, the projected longevity effect of device features to reduce atrial pacing and reduce ventricular pacing, and device characteristics such as battery size and high impedance leads (> or =1,000 ohms), was investigated.Atrial and RV manual versus automatic measurements were equivalent in 683 of 691 subjects (98.8%) and 736 of 746 subjects (98.7%), respectively. Thresholds were stable with 99.6% of atrial and 99.2% of RV consecutive measurements within +/-0.25V. Algorithms for threshold tracking, reducing ventricular pacing, and reducing atrial pacing were associated with 0.8, 0.9, and 0.2 years projected longevity improvements. High impedance leads were associated with a 0.8-year projected longevity improvement. Approximately 2 years of longevity improvement was projected for a 1-cc increase in device size.The atrial and RV algorithms were accurate and reliable in all leads tested. Threshold tracking, reduced ventricular pacing, and high impedance leads result in increased device longevity. Battery capacity was the strongest determinant of increased projected longevity.

Abstract

Together with pulmonary veins, many extrapulmonary vein areas may be the source of initiation and maintenance of atrial fibrillation. The left atrial appendage (LAA) is an underestimated site of initiation of atrial fibrillation. Here, we report the prevalence of triggers from the LAA and the best strategy for successful ablation.Nine hundred eighty-seven consecutive patients (29% paroxysmal, 71% nonparoxysmal) undergoing redo catheter ablation for atrial fibrillation were enrolled. Two hundred sixty-six patients (27%) showed firing from the LAA and became the study population. In 86 of 987 patients (8.7%; 5 paroxysmal, 81 nonparoxysmal), the LAA was found to be the only source of arrhythmia with no pulmonary veins or other extrapulmonary vein site reconnection. Ablation was performed either with focal lesion (n=56; group 2) or to achieve LAA isolation by placement of the circular catheter at the ostium of the LAA guided by intracardiac echocardiography (167 patients; group 3). In the remaining patients, LAA firing was not ablated (n=43; group 1). At the 12+/-3-month follow-up, 32 patients (74%) in group 1 had recurrence compared with 38 (68%) in group 2 and 25 (15%) in group 3 (P<0.001).The LAA appears to be responsible for arrhythmias in 27% of patients presenting for repeat procedures. Isolation of the LAA could achieve freedom from atrial fibrillation in patients presenting for a repeat procedure when arrhythmias initiating from this structure are demonstrated.

Abstract

Catheter ablation of atrial fibrillation is associated with the potential risk of periprocedural stroke, which can range between 1% and 5%. We developed a prospective database to evaluate the prevalence of stroke over time and to assess whether the periprocedural anticoagulation strategy and use of open irrigation ablation catheter have resulted in a reduction of this complication.We collected data from 9 centers performing the same ablation procedure with the same anticoagulation protocol. We divided the patients into 3 groups: ablation with an 8-mm catheter off warfarin (group 1), ablation with an open irrigated catheter off warfarin (group 2), and ablation with an open irrigated catheter on warfarin (group 3). Outcome data on stroke/transient ischemic attack and bleeding complications during and early after the procedures were collected. Of 6454 consecutive patients in the study, 2488 were in group 1, 1348 were in group 2, and 2618 were in group 3. Periprocedural stroke/transient ischemic attack occurred in 27 patients (1.1%) in group 1 and 12 patients (0.9%) in group 2. Despite a higher prevalence of nonparoxysmal atrial fibrillation and more patients with CHADS2 (congestive heart failure, hypertension, age >75 years, diabetes mellitus, and prior stroke or transient ischemic attack) score >2, no stroke/transient ischemic attack was reported in group 3. Complications among groups 1, 2, and 3, including major bleeding (10 [0.4%], 11 [0.8%], and 10 [0.4%], respectively; P>0.05) and pericardial effusion (11 [0.4%], 11 [0.8%], and 12 [0.5%]; P>0.05), were equally distributed.The combination of an open irrigation ablation catheter and periprocedural therapeutic anticoagulation with warfarin may reduce the risk of periprocedural stroke without increasing the risk of pericardial effusion or other bleeding complications.

Abstract

Total subcutaneous implantable subcutaneous defibrillators are in development, but optimal electrode configurations are not known.We used image-based finite element models (FEM) to predict the myocardial electric field generated during defibrillation shocks (pseudo-DFT) in a wide variety of reported and innovative subcutaneous electrode positions to determine factors affecting optimal lead positions for subcutaneous implantable cardioverter-defibrillators (S-ICD).An image-based FEM of an adult man was used to predict pseudo-DFTs across a wide range of technically feasible S-ICD electrode placements. Generator location, lead location, length, geometry and orientation, and spatial relation of electrodes to ventricular mass were systematically varied. Best electrode configurations were determined, and spatial factors contributing to low pseudo-DFTs were identified using regression and general linear models.A total of 122 single-electrode/array configurations and 28 dual-electrode configurations were simulated. Pseudo-DFTs for single-electrode orientations ranged from 0.60 to 16.0 (mean 2.65 +/- 2.48) times that predicted for the base case, an anterior-posterior configuration recently tested clinically. A total of 32 of 150 tested configurations (21%) had pseudo-DFT ratios =1, indicating the possibility of multiple novel, efficient, and clinically relevant orientations. Favorable alignment of lead-generator vector with ventricular myocardium and increased lead length were the most important factors correlated with pseudo-DFT, accounting for 70% of the predicted variation (R(2) = 0.70, each factor P < .05) in a combined general linear model in which parameter estimates were calculated for each factor.Further exploration of novel and efficient electrode configurations may be of value in the development of the S-ICD technologies and implant procedure. FEM modeling suggests that the choice of configurations that maximize shock vector alignment with the center of myocardial mass and use of longer leads is more likely to result in lower DFT.

Abstract

Cardiac resynchronization therapy improves morbidity and mortality in appropriately selected patients. Whether atrioventricular (AV) and interventricular (VV) pacing interval optimization confers further clinical improvement remains unclear. A variety of techniques are used to estimate optimum AV/VV intervals; however, the precision of their estimates and the ramifications of an imprecise estimate have not been characterized previously.An objective methodology for quantifying the precision of estimated optimum AV/VV intervals was developed, allowing physiologic effects to be distinguished from measurement variability. Optimization using multiple conventional techniques was conducted in individual sessions with 20 patients. Measures of stroke volume and dyssynchrony were obtained using impedance cardiography and echocardiographic methods, specifically, aortic velocity-time integral, mitral velocity-time integral, A-wave truncation, and septal-posterior wall motion delay. Echocardiographic methods yielded statistically insignificant data in the majority of patients (62%-82%). In contrast, impedance cardiography yielded statistically significant results in 84% and 75% of patients for AV and VV interval optimization, respectively. Individual cases demonstrated that accepting a plausible but statistically insignificant estimated optimum AV or VV interval can result in worse cardiac function than default values.Consideration of statistical significance is critical for validating clinical optimization data in individual patients and for comparing competing optimization techniques. Accepting an estimated optimum without knowledge of its precision can result in worse cardiac function than default settings and a misinterpretation of observed changes over time. In this study, only impedance cardiography yielded statistically significant AV and VV interval optimization data in the majority of patients.

Abstract

To assess whether treatment with statins or renin-angiotensin-aldosterone system (RAAS) inhibitors as potential procedural 'augmenting agents' improved atrial fibrillation (AF) catheter ablation recurrence rates in post-menopausal females (PMFS).Five hundred and eighteen consecutive female patients had undergone AF catheter ablation from January 2005 to May 2008. Post-menopausal females were selected and procedure outcomes were compared between cohorts of PMFS treated with statins or RAAS inhibitors to untreated PMFS. Out of 408 PMFS, 36 (8.8%) were treated with a combination of RAAS inhibitors and statins, thus were excluded leaving a total of 372 (91.2%) patients in the study. Out of 372 patients, 111 (29.8%) were on statins (Group 1), 59 (15.9%) on RAAS inhibitors (Group 2), and 202 (54.3%) without RAAS inhibitors or statins [(Group 3) control population]. Over a mean follow-up time of 24 +/- 8.3 (median 25) months, 78 (70.6%) in Group 1, 38 (65.4%) in Group 2, and 139 (68.8%) in Group 3 had procedural success. Statin or RAAS inhibitor use did not predict lower recurrence rates [hazard ratio (HR): 1.26, P = 0.282 and HR: 1.14, P = 0.728, respectively]. When compared with controls, no difference in the cumulative incidence of recurrence was found with statin or RAAS inhibitors use (P = 0.385 and P = 0.761, respectively).Treatment with statins or RAAS inhibitors did not improve catheter ablation success rates among PMFS. Thereby, from a clinical standpoint, PMFS should not be started on these treatments as a procedural 'augmenting agent' at this time.

Abstract

Most atrial fibrillation (AF) ablation studies have consisted predominantly of males; accordingly, there is a paucity of information on the safety and efficacy of catheter ablation in a large cohort of female AF patients.The purpose of this study was to evaluate catheter ablation for AF in female patients.From January 2005 to May 2008, 3265 females underwent pulmonary vein antrum isolation. Success rates, patient profiles, and complications were collected.Approximately 16% of our population was female (P

Abstract

Background. Currently there are no reliable predictors of response to cardiac resynchronization therapy (CRT) before implantation. We compared pre-CRT left ventricular (LV) dyssynchrony by tissue Doppler imaging (TDI) and regional volumetric analysis by 3-dimensional transthoracic echocardiography (3DTTE) in predicting response to CRT. Methods. Thirty-eight patients (79% nonischemic cardiomyopathy) with symptomatic heart failure who underwent CRT were enrolled. Clinical and echocardiographic responses were defined as improvement in one NYHA class and reduction in LV end-systolic volume by ?15% respectively. Functional status was assessed by Minnesota Living with Heart Failure questionnaire and 6-minute walk distance. Results. In 33 patients, after CRT for 7.86 ± 2.27 months, there were 24 (73%) clinical and 19 (58%) echocardiographic responders. Functional parameters, LV dimensions, volumes and synchrony by TDI and 3DTTE improved significantly in responders. There was no difference in the number of responders and nonresponders when cut-off values for dyssynchrony by different measurements validated in other trials were applied. Area under receiver-operating-characteristic curve ranged from 0.4 to 0.6. Conclusion. CRT improves clinical and echocardiographic parameters in patients with systolic heart failure. The dyssynchrony measurements by TDI and 3DTTE are not comparable and are unable to predict response to CRT.

Abstract

The advent of subcutaneous implantable cardioverter-defibrillator (ICD) systems represents a paradigm shift for the detection and therapy of ventricular tachyarrhythmias. Despite advances in transvenous lead technology, problems remain that notably include requirement for technical expertise; periprocedural complications during implantation and explantation; and long-term lead failure. Although subcutaneous ICD systems may mitigate some of these risks, they provide new shortcomings, such as inability to provide pacing therapy for bradyarrhythmias, ventricular tachyarrhythmias, and cardiac resynchronization. Ongoing clinical evaluation and development are required before the role of subcutaneous ICDs as an adjunctive or primary therapy can be defined. This article examines studies investigating the subcutaneous ICD and discusses its possible advantages and disadvantages as compared with current transvenous ICD systems.

Abstract

Atrial fibrillation (AF) is the most prevalent arrhythmia in the United States and accounts for more than 750,000 strokes per year. Noninvasive predictors of AF may help identify patients at risk of developing AF. Our objective was to identify the electrocardiographic characteristics associated with onset of AF.This was a retrospective cohort analysis of 42,751 patients with electrocardiograms (ECGs) ordered by physician's discretion and analyzed using a computerized system. The population was followed for detection of AF on subsequent ECGs. Cox proportional hazard regression analysis was performed to test the association between these ECG characteristics and development of AF.For a mean follow-up of 5.3 years, 1,050 (2.4%) patients were found to have AF on subsequent ECG recordings. Several ECG characteristics, such as P-wave dispersion (the difference between the widest and narrowest P waves), premature atrial contractions, and an abnormal P axis, were predictive of AF with hazard ratio of approximately 2 after correcting for age and sex. P-wave index, the SD of P-wave duration across all leads, was one of the strongest predictors of AF with a concordance index of 0.62 and a hazard ratio of 2.7 (95% CI 2.1-3.3) for a P-wave index >35. These were among the several independently predictive markers identified on multivariate analysis.Several ECG markers are independently predictive of future onset of AF. The P index, a measurement of disorganized atrial depolarization, is one of the strongest predictors of AF. The ECG contains valuable prognostic information that can identify patients at risk of AF.

Abstract

The efficacy of pulmonary vein isolation for the treatment of atrial fibrillation may be limited by the ability to make continuous and transmural lesions utilizing an ablation catheter. Gaps often persist between ablation lesions leading to failed electrical isolation and thus failed ablation. Recently, a deflectable fiberoptic endocardial visualization catheter has been introduced for use in imaging the coronary sinus using light in the visible spectrum. We utilize this catheter to visualize the endocardial surface and examine radiofrequency ablation lesions in porcine endocardium to determine the presence of gaps between radiofrequency lesions.Videos were taken of the lesions and shown to two readers who were asked to identify the gaps ranging from less than 0.1 mm-9.8 mm.Ninety-four lesion gaps were reviewed. The readers demonstrated a combined accuracy of 98.4% at identifying gaps.Gaps between ablation lesions can be accurately identified down to less than 1 mm distances in vitro using a direct visualization catheter. Further studies are warranted to confirm these finding in vivo.

Abstract

Responders to cardiac resynchronization therapy (CRT) have greater left ventricular (LV) dyssynchrony than nonresponders prior to CRT.We conducted this study to see whether the long term responders have more worsening of LV dyssynchrony and LV function on acute interruption of CRT.We identified 22 responders and 13 nonresponders who received CRT as per standard criteria for 23.73 +/- 7.9 months (median 24.5 months). We assessed the acute change in LV function, mitral regurgitation (MR) and compared LV dyssynchrony in CRT on and off modes.On turning off CRT, there was no significant worsening of LV dyssynchrony in both responders and nonresponders. The dyssynchrony measurements by SPWMD, TDI and 3D echocardiography did not correlate significantly. LVESV increased (p = 0.02) and MR (p = 0.01) worsened in CRT-off mode in responders only without significant change in LVEF or LV dimensions. Discussion andIn long-term responders to CRT, there is alteration in the function of remodeled LV with acute interruption of CRT, without significant worsening of LV dyssynchrony. The role of different echocardiographic parameters in the assessment of LV dyssynchrony remains controversial. Even after long-term CRT reversely remodels the LV, the therapy needs to be continued uninterrupted for sustained benefits.

Abstract

The proximity of the phrenic nerve (PN) to cardiac tissue relevant to arrhythmias may increase the risk of PN injury. Strategies for preventing PN injury in the pericardial space are limited.The purpose of this study was to compare methods for separating the PN from the epicardial surface in order to prevent PN injury.Eight patients referred for epicardial ablation of arrhythmias were enrolled in the study. All patients required ablation near the PN. Endocardial and epicardial access was obtained in all patients. A three-dimensional mapping system was used to guide mapping and ablation. All patients underwent epicardial catheter ablation. Pacing via the ablation catheter identified the location of the PN. In order to prevent PN injury, four new strategies were tested in each patient. We sought to increase the distance between the epicardium and the PN by (1) placing a large-diameter balloon between the nerve and the myocardium, (2) introducing saline in steps of 20 ml until PN capture was lost or blood pressure dropped below 60 mmHg, (3) introducing air until PN capture was lost or blood pressure dropped below 60 mmHg, or (4) introducing a combination of saline and air until PN capture was lost or blood pressure dropped below 60 mmHg.At each step, epicardial pacing was performed to assess for PN stimulation. The combination of air and saline resulted in the greatest decrease of PN stimulation. Saline only failed in all cases. Air only and balloon placement were infrequently successful.Controlled and progressive inflation of air and saline together with careful monitoring of hemodynamic parameters appears to be the best strategy for preventing PN injury during epicardial ablation. Placement of a large balloon in the appropriate location can be difficult.

Abstract

Effective ablation of atrial fibrillation and other cardiac arrhythmias requires precise catheter navigation and controlled delivery of energy to cardiac tissue. In this study, we summarize our initial experience using a fiber optic direct visualization catheter to evaluate and guide placement of endocardial radiofrequency (RF) ablation lesions. RF lesions were created in cadaveric porcine hearts and examined in a blood-filled field using a direct visualization catheter. Direct visualization of RF lesions was repeated in vivo using an ovine model. Lesions and interlesion gaps were clearly identifiable using the direct visualization catheter. It was possible to place lesions in proximity to anatomical landmarks and in relation to one another. Catheter-generated images correlated well with lesion appearance on gross examination. Direct catheter-based visualization is a feasible technique for guiding RF lesion placement, estimating lesion size, and identifying interlesion gaps. Future work is needed to correlate surface appearance with transmurality and electrical isolation.

Abstract

Sudden cardiac death among orthotopic heart transplant recipients is an important mechanism of death after cardiac transplantation. The role for implantable cardioverter-defibrillators (ICDs) in this population is not well established. This study sought to determine whether ICDs are effective in preventing sudden cardiac death in high-risk heart transplant recipients.We retrospectively analyzed the records of all orthotopic heart transplant patients who had ICD implantation between January 1995 and December 2005 at 5 heart transplant centers. Thirty-six patients were considered high risk for sudden cardiac death. The mean age at orthotopic heart transplant was 44+/-14 years, the majority being male (n=29). The mean age at ICD implantation was 52+/-14 years, whereas the average time from orthotopic heart transplant to ICD implant was 8 years +/-6 years. The main indications for ICD implantation were severe allograft vasculopathy (n=12), unexplained syncope (n=9), history of cardiac arrest (n=8), and severe left ventricular dysfunction (n=7). Twenty-two shocks were delivered to 10 patients (28%), of whom 8 (80%) received 12 appropriate shocks for either rapid ventricular tachycardia or ventricular fibrillation. The shocks were effective in terminating the ventricular arrhythmias in all cases. Three (8%) patients received 10 inappropriate shocks. Underlying allograft vasculopathy was present in 100% (8 of 8) of patients who received appropriate ICD therapy.Use of ICDs after heart transplantation may be appropriate in selected high-risk patients. Further studies are needed to establish an appropriate prevention strategy in this population.

Abstract

Whether different ablation strategies affect paroxysmal atrial fibrillation (AF) long-term freedom from AF/atrial tachyarrhythmia is unclear. We sought to compare the effect of 3 different ablation approaches on the long-term success in patients with paroxysmal AF.One hundred three consecutive patients with paroxysmal AF scheduled for ablation and presenting in the electrophysiology laboratory in AF were selected for this study. Patients were randomized to pulmonary vein antrum isolation (PVAI; n=35) versus biatrial ablation of the complex fractionated atrial electrograms (CFAEs; n=34) versus PVAI followed by CFAEs (n=34). Patients were given event recorders and followed up at 3, 6, 9, 12, and 15 months postablation. There was no statistical significant difference between the groups in term of sex, age, AF duration, left atrial size, and ejection fraction. At 1 year follow-up, freedom from AF/atrial tachyarrhythmia was documented in 89% of patients in the PVAI group, 91% in the PVAI plus CFAEs group, and 23% in the CFAEs group (P<0.001) after a single procedure and with antiarrhythmic drugs.No difference in terms of success rate was seen between PVAI alone and PVAI associated with defragmentation. CFAEs ablation alone had the smallest impact on AF recurrences at 1-year follow-up. These results suggest that antral isolation is sufficient to treat most patients with paroxysmal AF.

Abstract

Popping, char and perforation are complications that can occur following catheter ablation. We measured the amount of grams (g) applied to the endocardium during ablation using a sensor incorporated in the long sheath of a robotic system. We evaluated the relationship between lesion formation, pressure, and the development of complications.Using a robotic navigation system, lesions were placed in the left atrium (LA) at six settings, using a constant duration (40 seconds) and flow rate of either 17 cc/min or 30 cc/min with an open irrigated catheter (OIC). Evidence of complications was noted and lesion location recorded for later analysis at necropsy.Lesions using 30 Watts (W) were more likely to be transmural at higher (>40 g) than lower (<30 g) pressures (75% vs 25%, P < 0.001). Significantly higher number of lesions using >40 g of pressure demonstrated "popping" and crater formation as compared with lesions with 20-30 g of pressure (41% vs 15%, P = 0.008). A majority of lesions placed using higher power (45 W) with higher pressures (>40 g) were associated with char and crater formation (66.7%). No lesions using 10 g of pressure were transmural, regardless of the power. Lesions placed with a power setting less than 35 W were more likely to result in "relative" sparing of the endocardial surface than lesions at a power setting higher than 35 W (62% vs 33.3%, P = 0.02) regardless of the pressure.When using an OIC, lower power settings (

Abstract

Premature ventricular complexes (PVCs) during exercise are associated with adverse prognosis, particularly in patients with intermediate treadmill test findings. Statin use reduces the incidence of resting ventricular arrhythmias in patients with coronary artery disease; however, the relationship between statin use and exercise-induced ventricular arrhythmias has not been investigated.We evaluated the association between statin use and PVCs in 1,847 heart-failure-free patients (mean age 58, 95% male) undergoing clinical exercise treadmill testing between 1997 and 2004 in the VA Palo Alto Health Care System. PVCs were quantified in beats per minute and frequent PVCs were defined as PVC rates greater than the median value (0.43 and 0.60 PVCs per minute for exercise and recovery, respectively). Propensity-adjusted logistic regression was used to evaluate the odds of developing PVCs during exercise and recovery periods associated with statin use. There were 431 subjects who developed frequent PVCs during exercise and 284 subjects had frequent recovery PVCs. After propensity score adjustment, subjects treated with statins (n = 145) had 42% lower odds of developing frequent PVCs during exercise (odds ratio [OR] 0.58, 95% confidence interval [CI] 0.37-0.93) and 44% lower odds of developing frequent PVCs during recovery (OR 0.56, 95% CI 0.30-0.94). These effects were not modified by age, prior coronary disease, hypercholesterolemia, exercise-induced angina, or exercise capacity.Statin use was associated with reduced odds of frequent PVCs during and after clinical exercise testing in a manner independent of associations with coronary disease or ischemia in our study population.

Abstract

Inappropriate shocks due to misclassification of supraventricular and ventricular arrhythmias remain a major problem in the care of patients with Implantable Cardioverter Defibrillators (ICDs). The purpose of this study was to investigate the ability of a new covariance-based support vector machine classifier, to distinguish ventricular tachycardia from other rhythms such as supraventricular tachycardia. The proposed algorithm is applicable on both single and dual chamber ICDs and has a low computational demand. The results demonstrate that suggested algorithm has considerable promise and merits further investigation.

Abstract

Pulmonary-vein isolation is increasingly being used to treat atrial fibrillation in patients with heart failure.In this prospective, multicenter clinical trial, we randomly assigned patients with symptomatic, drug-resistant atrial fibrillation, an ejection fraction of 40% or less, and New York Heart Association class II or III heart failure to undergo either pulmonary-vein isolation or atrioventricular-node ablation with biventricular pacing. All patients completed the Minnesota Living with Heart Failure questionnaire (scores range from 0 to 105, with a higher score indicating a worse quality of life) and underwent echocardiography and a 6-minute walk test (the composite primary end point). Over a 6-month period, patients were monitored for both symptomatic and asymptomatic episodes of atrial fibrillation.In all, 41 patients underwent pulmonary-vein isolation, and 40 underwent atrioventricular-node ablation with biventricular pacing; none were lost to follow-up at 6 months. The composite primary end point favored the group that underwent pulmonary-vein isolation, with an improved questionnaire score at 6 months (60, vs. 82 in the group that underwent atrioventricular-node ablation with biventricular pacing; P<0.001), a longer 6-minute-walk distance (340 m vs. 297 m, P<0.001), and a higher ejection fraction (35% vs. 28%, P<0.001). In the group that underwent pulmonary-vein isolation, 88% of patients receiving antiarrhythmic drugs and 71% of those not receiving such drugs were free of atrial fibrillation at 6 months. In the group that underwent pulmonary-vein isolation, pulmonary-vein stenosis developed in two patients, pericardial effusion in one, and pulmonary edema in another; in the group that underwent atrioventricular-node ablation with biventricular pacing, lead dislodgment was found in one patient and pneumothorax in another.Pulmonary-vein isolation was superior to atrioventricular-node ablation with biventricular pacing in patients with heart failure who had drug-refractory atrial fibrillation. (ClinicalTrials.gov number, NCT00599976.)

Abstract

Expansion of indications for implantable cardioverter-defibrillators (ICDs) has led to a significant increase in the number of patients receiving ICDs and the number of lives saved because of ICD therapy. However, appropriate or inappropriate shocks are frequent and may result in a significant decrease in quality of life in patients with ICDs. Atrial fibrillation with rapid ventricular response, sinus tachycardia, atrial tachycardia or atrial flutter with rapid conduction, and other supraventricular tachycardias are the most common arrhythmias causing inappropriate therapy. Other causes include oversensing of diaphragmatic potentials or myopotentials, T-wave oversensing, double or triple counting of intracardiac signals, lead fractures or header connection problems, lead chatter or noise, and electromagnetic interference. Strategies to reduce inappropriate therapy using device programming rely on the ability to distinguish supraventricular and atrial arrhythmias from ventricular tachycardia. Avoiding therapy for nonsustained ventricular arrhythmias and increasing the role of antitachycardia pacing to terminate ventricular tachycardia are key approaches to reducing shocks for ventricular arrhythmias. Optimal programming holds great promise for decreasing the overall incidence of shock therapy and increasing ICD acceptance.

Abstract

Diseases of the electrical conduction system that lead to irregularities in cardiac rhythm can have morbid and often lethal clinical outcomes. Linkage analysis has been the principal tool used to discover the genetic mutations responsible for Mendelian arrhythmic disease. Although the majority of arrhythmias can be accounted for by mutations in genes encoding ion channels, linkage analysis has also uncovered the role of other gene families such as those encoding members of the desmosome. With a list of candidates in mind, mutational analysis has helped confirm the suspicion that proteins found in caveolae or gap junctions also play a role in arrhythmogenesis. Atrial fibrillation and sudden cardiac death are relatively common arrhythmias that may be caused by multiple factors including common genetic variants. Genome-wide association studies are already revealing the important and poorly understood role of intergenic regions in atrial fibrillation. Despite the great advancements that have been made in our understanding of the genetics of these diseases, we are still far from able to routinely use genomic data to make clinical management decisions. There remain several hurdles in the study of genetics of arrhythmia, including the costs of genotyping, the need to find large affected families for linkage analysis, or to recruit large numbers of patients for genome-wide studies. Novel techniques that incorporate epigenetic information, such as known gene-gene interactions, biologic pathways, and experimental gene expression, will need to be developed to better interpret the large amount of genetic data that can now be generated. The study of arrhythmia genetics will continue to elucidate the pathophysiology of disease, help identify novel therapies, and ultimately allow us to deliver the individualized medical therapy that has long been anticipated.

Abstract

Cardiac computed tomography (CT) is commonly used to visualize left atrial (LA) anatomy for ablation of atrial fibrillation. We have developed a new imaging technique that allows acquisition and visualization of three-dimensional (3D) cardiac images in the catheter lab.We sought to compare LA and pulmonary vein (PV) dimensions acquired using gated multisweep rotational fluoroscopy (C-arm CT) system and multislice computed tomography (MSCT) in an in vivo porcine model.A Siemens AXIOM Artis dTA C-arm system (Siemens AG, Medical Solutions) was modified to allow acquisition of four bidirectional sweeps during synchronized acquisition of the electrocardiogram signal to allow retrospective gating. C-arm CT image volumes were then reconstructed. Gated MSCT (SOMATOM Sensation 16 and 64, Siemens AG, Medical Solutions) and C-arm CT images were acquired in six animals. The two main PV diameters were measured in orthogonal axes. LA volumes were calculated. C-arm CT measurements were compared with the MSCT measurements.The average PV diameters using the C-arm CT were 2.24 x 1.35 cm, versus 2.27 x 1.38 cm for CT. The average difference was 0.034 cm (1.9%) between the C-arm CT and standard CT. The average LA volume using MSCT was 49.1 +/- 12.7 cm(3), as compared with 51.0 +/- 8.7 cm(3) obtained by the C-arm CT. The average difference between the C-arm CT and the MSCT was 1.9 cm(3) (3.7%). There were no significant differences in either the PV or LA measurements.Visualization of 3D cardiac anatomy during ablation procedures is possible and highly accurate. The 3D cardiac reconstructions acquired during ablation procedures will be valuable for procedural planning and guidance.

Abstract

Inappropriate shocks due to misclassification of supraventricular and ventricular arrhythmias remain a major problem in the care of patients with Implantable Cardioverter defibrillators (ICDs). In this study we have investigated the ability of a new covariance-based algorithm, to distinguish Ventricular Tachycardia from other rhythms such as Supraventricular Tachycardia. The proposed algorithm has a low computational demand and with a small adjustment is applicable on both single-chamber and dual-chamber ICDs. The results are promising and suggest that the new covariance-based algorithm may be an effective method for ICD rhythm classification and may decrease inappropriate shocks.

Abstract

The precise reasons for failure to cannulate the coronary sinus during biventricular device implantation are unknown. Visualization of the coronary sinus ostium during electrophysiology procedures may enhance understanding of how unusual anatomy can affect successful cannulation of the coronary sinus.The aim of this study was to describe the morphology of valves at the coronary sinus ostium (CSO) visualized directly with an illuminated fiberoptic endoscope during implantation of biventricular devices.The coronary sinus anatomy of one hundred consecutive patients undergoing implantation of biventricular devices was investigated using a fiberoptic endocardial visualization catheter (EVC).The CSO was clearly visualized in 98 patients using the EVC. A Thebesian valve was seen in 54% of these. Almost all Thebesian valves were positioned at the inferior (61%) or posterior (33%) aspect of the CSO. Only six patients had Thebesian valves that covered more than 70% of the CSO, but all were successfully implanted with a transvenous left ventricular pacing lead after cannulating the coronary sinus under direct visualization.Over half of patients undergoing biventricular device implantation have identifiable Thebesian valves. Even valves covering the majority of the ostial area may be traversed using direct visualization and modern catheterization techniques.

Abstract

This study examined the risk of implantable cardioverter-defibrillator (ICD) shocks for ventricular tachycardia (VT) or ventricular fibrillation (VF) associated with driving.Concerns regarding VT/VF occurring during driving are the basis for driving restrictions in ICD patients; however, limited data are available to inform recommendations.This study used a prospective nested case-crossover design to compare the risk of ICD shock for VT/VF both during and up to 60 min after an episode of driving as compared with that during other activities among 1,188 ICD patients enrolled in the TOVA (Triggers of Ventricular Arrhythmia) study.Over a median follow-up of 562 days, there were 193 ICD shocks for VT/VF with data on exposure to driving before ICD shock. The absolute risk of ICD shock for VT/VF within 1 h of driving was estimated to be 1 episode per 25,116 person-hours spent driving. The ICD shocks for VT/VF were twice as likely to occur within 1 h of driving a car as compared with other times (relative risk [RR] 2.24, 95% confidence interval [CI] 1.57 to 3.18). This risk was specific for shocks for VT/VF and occurred primarily during the 30-min period after driving (RR 4.46, 95% CI 2.92 to 6.82) rather than during the driving episode itself (RR 1.05, 95% CI 0.48 to 2.30).Although the risk of ICD shock for VT/VF was transiently increased in the 30-min period after driving, the risk was not elevated during driving and the absolute risk was low. These data provide reassurance that driving by ICD patients should not translate into an important rate of personal or public injury.

Abstract

Implantation of pacemakers and implantable cardioverter-defibrillators (ICDs) can be complicated by infection and device erosion. It is unclear if the clinical features of patients who have device erosion differ from those without erosion.We retrospectively examined the records of all patients referred for explantation of a pacemaker or defibrillator from January 2000 to May 2005. We examined demographic variables including age, gender, and body mass index (BMI) as well as clinical variables related to erosion and procedural variables.Seventy-two patients with infected pacemakers or ICDs were identified. Of these cases, 30 (42%) developed infection complicated by erosion, of which 8/28 (29%) were related to ICDs, and 22/44 (50%) were related to pacemakers.Device erosion was significantly associated with the presence of a non-systemic infection as opposed to cases without erosion. This finding may have implications in the timing of device re-implantation.

Abstract

As heart disease is increasingly recognized in women and as important studies have elucidated the benefit of implantable cardioverter defibrillators (ICDs) in patients with nonischemic cardiomyopathy (NICM), little is known regarding the effect of gender difference on arrhythmic risk in this population. We sought to determine if there are gender differences in arrhythmic risk and potential defibrillator benefit in patients with NICM.The records of 767 consecutive patients who underwent ICD implant at the Stanford Medical Center from 1984 to 2002 were reviewed. Only patients with NICM were considered (n = 201, 26.2%). Of these, 140 patients had clinical follow-up information available. Baseline variables were examined, including age, baseline heart rate, ejection fraction, and medications. We evaluated the time to first shock as well as all-cause mortality in this patient population. Kaplan-Meier survival curves were plotted, a log-rank test was used to evaluate significance, and Cox-proportional hazards test was used for multivariate analysis.There were 88 (62.9%) men and 52 (37.1%) women. Between male and female patients, there were no significant differences in baseline mean age (54.8 +/- 1.9 years vs 53.1 +/- 2.3 years, respectively), ejection fraction (35.2 +/- 2.0% vs 33.3 +/- 2.3%, respectively), and mean left ventricular end-diastolic dimension (6.4 +/- 0.3 cm vs 5.9 +/- 0.2 cm, respectively). Mean follow-up time was 30.8 months. Thirty-two male patients (36.4 +/- 0.05%) received appropriate shocks compared with 20 female patients (38.5 +/- 0.07%). Mean time to the first appropriate shock was 11.9 +/- 3.9 months for male patients and 21.3 +/- 5.8 months for female patients (P = 0.2). Nineteen male patients (21.6 +/- 0.05%) died or received heart transplant during the follow-up period compared with 6 female patients (11.5 +/- 0.04%) (P = 0.11).Male and female patients with NICM who received ICDs had similar rate of appropriate shock and mortality. In this population gender does not appear to be an important risk factor for mortality or arrhythmic events.

Abstract

Inappropriate shock remains a major issue in patients with implantable cardioverter defibrillators. We examine an inappropriate shock delivered in a patient with atrial tachycardia that conducted 1:1. We reconstruct the device algorithms that led to therapy delivery and discuss programming changes that could be considered.

Abstract

Giant cell myocarditis (GCM) is an uncommon disorder that affects ventricular myocardium causing severe left ventricular dysfunction and ventricular arrhythmias. We report a case of GCM that only affected the atrium sparing the ventricle.

Abstract

Despite improvements in cardiac resynchronization therapy (CRT) implantation techniques, a significant minority of CRT attempts are unsuccessful. Inability to cannulate the coronary sinus (CS) because of difficult anatomy is a major reason for unsuccessful CRT implantation. Direct visualization of intracardiac structures during the implant may facilitate access into the CS. The present study describes CRT implantation with the aid of an endocardial visualization catheter (EVC).Fifty-eight consecutive patients (mean age 72 +/- 12 years; ejection fraction 26.2% +/- 7.0%; New York Heart Association [NYHA] class 2.9) underwent CRT implantation using a steerable fiberoptic EVC (Acumen Medical, Inc., Sunnyvale, CA).The EVC was able to visualize the CS ostium in all cases. The CS was successfully cannulated in 57 (98.3%) of 58 patients. The time from vascular access to CS visualization was 6 +/- 5 minutes, and the total time to CS access was 8 +/- 6 minutes. Successful left ventricle (LV) lead implantation was accomplished in 55 (94.8%) of 58 patients. Three patients who had a previous history of failed LV lead implantation were successfully implanted using the EVC.Fiberoptic imaging of intracardiac structures during CRT implantation may be performed rapidly in a wide range of patients with an EVC. The ability to visualize right atrial anatomy may aid CS access and LV lead implantation.

Abstract

Orthotopic heart transplantation is considered an effective treatment for patients with refractory heart failure. The long-term survival of orthotopic heart transplantation recipients has increased over the last several decades, but many long-term survivors of orthotopic heart transplantation develop graft atherosclerosis and associated left ventricular dysfunction. The risk of sudden cardiac death in long-term survivors of orthotopic heart transplantation with these complications is believed to be high. There are no data on the usefulness of implantable cardioverter-defibrillators (ICDs) in this population; therefore, we report our early experience with ICD placement in such patients.The purpose of this study was to examine the use of ICDs in adults who are long-term survivors of heart transplantation.We retrospectively reviewed all adult patients who underwent orthotopic heart transplantation at Stanford University Hospital (Stanford, CA, USA) from 1980 to 2004. All patients who received an ICD after transplant were included in this study. We reviewed demographic data, medical history, ejection fraction, presence of graft atherosclerosis, indication for ICD placement, and any device therapy delivered.Of the 925 patients who had orthotopic heart transplantation during this time period, 493 patients were alive at the beginning of the year 2000. Of these patients, 10 ( approximately 2%) had subsequent placement of an ICD. All 10 patients were male. The average age at orthotopic heart transplantation was 37.8 years. The average age at ICD placement was 50.5 years. The average time from orthotopic heart transplantation to ICD placement was 14.6 years. The average ejection fraction at the time of implant was 46.5%. Five of the 10 patients had a low ejection fraction (within this subgroup, the average ejection fraction was 31%, range 15%-45%) and graft atherosclerosis. ICDs were placed because of symptomatic episodes of ventricular tachycardia (3 patients), low ejection fraction and severe graft atherosclerosis without symptoms (3 patients), and after thorough evaluation for otherwise unexplained syncope (4 patients). The average follow-up after device implantation was 13 months. Complications related to ICD placement were an infected ICD system requiring explant in one patient and a lead fracture in another patient. Three patients had subsequent appropriate shocks for ventricular arrhythmias, and one patient underwent a second orthotopic heart transplantation. One patient died of malignancy.Use of the ICD in long-term survivors of orthotopic heart transplantation should be considered in appropriately selected patients. Further data are needed regarding ICD use in this population.

Abstract

We sought to examine the relationship between symptoms of depression and shock-treated ventricular arrhythmias among implantable cardioverter-defibrillator (ICD) patients.Depression predicts mortality in patients with coronary artery disease (CAD), but whether this is via an increased risk of fatal ventricular arrhythmias is unclear.We prospectively analyzed data on symptoms of depression and risk of ventricular arrhythmia (ventricular tachycardia/ventricular fibrillation [VT/VF]) resulting in ICD discharge in the Triggers of Ventricular Arrhythmias (TOVA) study. Symptoms were assessed by the Center for Epidemiologic Studies-Depression (CES-D) scale. Scores of 16 to 26 and > or =27 represented mild and moderate/severe depression, respectively. The Cox and Anderson-Gill proportional hazards models were used to test for associations among all patients and patients with CAD.Among 645 patients with baseline assessments, 90 (14%) were mildly depressed and 25 (3.9%) were moderately to severely depressed. Moderate/severe depression was associated with time to first shock for VT/VF (hazard ratio [HR] 3.2, 95% confidence interval [CI] 1.1 to 9.9) and all shocks for VT/VF including recurrent episodes (HR 3.2, 95% CI 1.2 to 8.6). Among the 476 CAD patients, the association with time to first shock (HR 6.4, 95% CI 1.9 to 21.1) and all shocks (HR 8.3, 95% CI 2.9 to 23.3) remained. The risk of shock for VT/VF was associated with depression severity in the total population (p for trend = 0.02) and among patients with CAD (p < 0.01), even after controlling for multiple confounders.More severe symptoms of depression predict shocks for VT/VF among ICD patients. The elevated risk of VT/VF among patients with CAD and depression suggests that arrhythmia may contribute significantly to total mortality in this subgroup.

Abstract

ST depression and T-wave amplitude abnormalities are known to be independent predictors of cardiovascular (CV) death, but a direct comparison between them has not been described.Analyses were performed on the first electrocardiogram (ECG) digitally recorded on 46,950 consecutive patients at the Palo Alto Veterans Affairs Medical Center since 1987. Females and patients with electrocardiograms exhibiting bundle branch block, left ventricular hypertrophy, electronic pacing, diagnostic Q waves, or Wolff-Parkinson-White syndrome were excluded, leaving 31,074 male patients for analysis (mean age 55 +/- 14). There were 1878 (6.0%) cardiovascular deaths (mean follow-up of 6 +/- 4 years). Electrocardiograms were classified using Minnesota code according to the degree of ST depression and T-wave abnormality, and the nine possible combinations of ST segment and T-wave abnormalities were recoded for analysis.The combination of major abnormalities in ST segments and T-waves carried the greatest hazard [3.2 (CI 2.7-3.8)]. Minor ST depression combined with more severe T-wave abnormalities carried a hazard of 3.1 (CI 2.5-3.7), whereas minor T-wave abnormalities combined with more severe ST depression carried a hazard of only 1.9 (CI 1.6-2.3).While both ST segment depression and abnormal T-wave amplitude are clinically important, T-wave abnormalities appear to be greater predictors of cardiovascular mortality.

Abstract

Recently, the use of robotic assisted surgery has been utilized in cardiac surgical procedures. The use of robotics may offer benefits in precision, stability and control of instruments remotely. We report early experience with a novel remote robotic catheter control system (CCS).We used a computerized robotically controlled catheter system that enables the user to remotely manipulate the tip of a catheter precisely in three dimensions. We tested the robotic catheter control systems ability to navigate within the heart and to make precise, rapid and repeatable movements. We compared the CCS with the ability of a standard quadripolar steerable ablation catheter placed in a deflectable sheath to navigate and make precision movements. Twelve ex-vivo porcine hearts were utilized to permit accurate measurements of navigation and precision. Eight targets were selected for navigation and precision testing. Time was measured for the catheter to reach the predefined target from a specific starting point to test navigation. In addition, time was measured to contact a discrete 0.8 mm target in order to test precision.The use of the CCS reduced the time needed for both navigation (8.5 +/- 13.9 sec vs. 22.7 +/- 26.7 sec, p = 0.002) and significantly decreased the time for precision targeting (10.1 +/- 6.9 sec vs. 29.6 +/- 26.4 sec, p < 0.001) in the specific RA and LA sites in the ex-vivo hearts.The use of a computerized robotically assisted catheter control system is feasible and shows promise in rapid precision movement of the catheter. Further study is needed to elucidate the role of such a system in-vivo and in patient specific catheter ablation and mapping.

Abstract

The purpose of this study was to validate the prognostic value of computer-derived measurements of the spatial alignment of ventricular depolarization and repolarization from the standard 12-lead ECG in a general medical population.Analyses were performed on the first ECG digitally recorded from 46,573 consecutive patients since 1987. QRS and T vector were synthesized by deriving XYZ leads from the 12 leads using the inverse Dower weighting matrix. Subset analyses were considered in patients with and those without standard ECG diagnoses (i.e., atrial fibrillation, Q waves, left ventricular hypertrophy, prolonged QRS duration). The main outcome measure was cardiovascular mortality.During a mean follow-up of 6 years, 4,127 cardiovascular deaths occurred. After adjusting for age, heart rate, and gender in a Cox regression analysis, spatial QRS-T angle was the most significant predictor of cardiovascular mortality, outperforming all other ECG measurements and diagnostic statements. In the subset with ECGs free of any standard diagnoses, annual cardiovascular mortality was 0.8% for normal (0-50 degrees ), 2.3% for borderline (50-100 degrees ), and 5.1% for abnormal (100-180 degrees ) QRS-T angle groups. The borderline and abnormal angle groups had 1.5- and 1.9-fold higher risk, respectively, relative to the normal QRS-T angle group after adjustment for age, gender, and heart rate. Similar results were found when patients with standard ECG diagnosis were included or compared.Spatial QRS-T angle is a significant and independent predictor of cardiovascular mortality that provides greater prognostic discrimination than any of the commonly utilized ECG diagnostic classifications.

Abstract

Among the most compelling challenges facing cardiologists today is identification of which patients are at highest risk for sudden death. Automatic implantable cardioverter-defibrillators are now indicated in many of these patients, yet the role of noninvasive risk stratification in classifying patients at high risk is not well defined. The purpose of this review is to evaluate the various electrocardiographic (ECG) techniques that appear to have potential in assessment of risk for arrhythmia. The resting ECG (premature ventricular contractions, QRS duration, damage scores, QT dispersion, and ST segment and T wave abnormalities), T wave alternans, late potentials identified on signal-averaged ECGs, and heart rate variability are explored. Unequivocal evidence to support the widespread use of any single noninvasive technique is lacking; further research in this area is needed. It is likely that a combination of risk evaluation techniques will have the greatest predictive power in enabling identification of patients most likely to benefit from device therapy.

Abstract

Cardiovascular screening of athletes is a challenging aspect of the preparticipation evaluation. While sudden cardiac death in young athletes is uncommon, preparticipation screening may identify some predisposing conditions that place individuals at increased risk. The most common pre-existing cardiac abnormalities in athletes causing sudden death in the United States are hypertrophic cardiomyopathy, congenital coronary anomalies, and Marfan syndrome. Preparticipation cardiovascular screening should pursue any history of cardiac symptoms or family history of premature cardiac disease, as well as abnormal cardiovascular physical findings. Positive findings should be investigated; an electrocardiogram, echocardiogram, or consultation with a specialist should be considered. Recommendations are then available to guide athletic participation according to the cardiovascular diagnosis.

Abstract

Left ventricular ejection fraction (LVEF) predicts device discharges in patients with implantable cardioverter-defibrillators (ICDs). The relationship between severity of congestive heart failure (CHF) and ICD discharges is less clear.We prospectively analyzed the association between CHF and risk of appropriate ICD discharges in the Triggers Of Ventricular Arrhythmias (TOVA) study, a cohort study of ICD patients conducted at 31 centers in the United States. Reported shocks were confirmed for sustained ventricular tachycardia (VT) or fibrillation (VF) by analysis of stored electrograms. Proportional hazards models included CHF categorized by New York Heart Association class. Baseline CHF was present among 502 (44%) of 1140 patients; 170 (34%) had class I, 230 (46%) had class II, 97 (19%) had class III, and only 5 (1%) had class IV symptoms. During median follow-up of 212 days, 92 patients experienced 1 or more appropriate ICD discharges. Class III CHF was associated in a statistically significantly manner with ICD discharge for VT/VF (hazard ratio 2.40, 95% CI 1.16 to 4.98), even with adjustment for LVEF. The combination of LVEF <0.20 and class III symptoms resulted in a particularly high risk of shocks for VT/VF (hazard ratio 3.90, 95% CI 1.28 to 11.92).Class III CHF, an easily accessible clinical measure, is an independent risk factor, along with LVEF, for ventricular arrhythmias that require shock therapy among ICD patients. Whether patients with class III CHF benefit to a greater degree from ICDs and whether aggressive treatment of CHF in ICD patients may prevent ventricular arrhythmias remains to be determined.

Abstract

Biventricular pacing has emerged as a modality for treatment of patients with heart failure. Combined biventricular pacers and implantable cardioverter defibrillators offer treatment of heart failure as well as protection from sudden cardiac death. However, inappropriate ICD shocks as a result of double sensing due to widely spaced ventricular bipoles may pose a significant problem in these patients. We examined the ICD records of twenty-three patients with biventricular ICDs, and evaluated all episodes of double sensing that resulted in aborted or delivered therapy. In follow-up of 3.7 +/- 2.6 months, thirty-three shocks in fifteen episodes occurred in five patients (21.7%) due to double sensing. Four patients (17.4%) had aborted shocks due to double sensing. All episodes resulting in shock occurred because of sinus tachycardia or supraventricular tachycardia above the upper programmed pacing rate of the device with resultant AV conduction and double sensing of the nonpaced ventricular depolarization. In conclusion, double sensing of the R-wave is a common and clinically important cause of inappropriate ICD detection and shock in patients with biventricular ICDs. Appropriate programming of the ICD can prevent episodes of inappropriate shocks.

Abstract

Arrhythmia management has undergone a revolution in the past decade. The diagnosis and treatment of arrhythmias in the athlete can be complicated by the need to compete and exercise. Some arrhythmias may be benign and asymptomatic, but others may be life threatening. Sinus bradyarrhythmias are common and even expected in athletes; these are rarely a cause for concern. Heart block is unusual and merits a thorough work-up. Atrial fibrillation may be more common in the athlete, and supraventricular tachycardias other than atrial fibrillation warrant consideration of radiofrequency ablation for cure. Ventricular arrhythmias in the athlete generally occur in the setting of structural heart disease that is genetically determined (hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, anomalous coronary arteries), or acquired (coronary artery disease, myocarditis, idiopathic dilated cardiomyopathies). In these conditions the arrhythmia is life threatening. Ventricular arrhythmias that occur in the athlete without structural heart disease are not thought to be life threatening. Athletes with structural heart disease and those with exertional syncope merit a complete evaluation.

Abstract

Implantable cardioverter defibrillators (ICDs) have become an important therapeutic modality for patients who have had a cardiac arrest or are at risk for life-threatening ventricular arrhythmias. Clinical trials have confirmed the role of the ICD for patients with sustained ventricular arrhythmias and have expanded the indications to include patients with coronary artery disease, left ventricular dysfunction, nonsustained ventricular tachycardia, and inducible ventricular tachycardia. Numerous technologic advances in ICDs have resulted in decreased size, greater ease of placement, and increased functionality. Important advancements have been made in the effectiveness of arrhythmia classification and electrogram storage. Dual-chamber ICDs have become increasingly sophisticated with rate-adaptive sensors. Biventricular pacing is being combined with ICD function in patients with heart failure, systolic dysfunction, and QRS widening. Future advances in devices will likely lead to improved arrhythmia classification, more advanced automated features, and additional features including more sophisticated sensors and biventricular pacing systems.

Abstract

ECGs and cardiac rhythms of normal athletes can vary widely. The heightened vagal tone from athletic conditioning can result in variant ECG findings that may mimic serious disorders. ECG patterns of long-QT syndrome, arrhythmogenic right ventricular dysplasia, Wolff-Parkinson-White syndrome, and hypertrophic cardiomyopathy signal the need for further evaluation, therapy, and possible participation restriction. Radiofrequency ablation may be appropriate when symptomatic supraventricular arrhythmias or Wolff-Parkinson-White syndrome is present. Further research is needed to effectively distinguish normal ECG changes in the athlete from changes that underlie cardiac disease. Improvements in identifying athletes at risk of serious or life-threatening arrhythmias are also needed.

Abstract

Cardiac arrhythmias in the athlete are a frequent cause for concern. Some arrhythmias may be benign and asymptomatic, but others may be life threatening and a sign that serious cardiovascular disease is present. Physicians often are consulted with regard to arrhythmias, or symptoms consistent with arrhythmias, in athletes. Sinus bradyarrhythmias are common and even expected in athletes. These bradyarrhythmias are rarely a cause for concern. Heart block is unusual and merits a thorough workup. Atrial fibrillation may be more common in the athlete. Supraventricular tachycardias other than atrial fibrillation generally warrant consideration of radiofrequency ablation for cure of the tachyarrhythmia. Ventricular arrhythmias in the athlete generally occur in the setting of structural heart disease that is genetically determined (hypertrophic cardiomyopathy, arrhythmogenic right ventricular dysplasia, anomalous coronary arteries) or acquired (coronary artery disease, myocarditis, idiopathic dilated cardiomyopathies). In these conditions, the arrhythmia generally is life threatening. Ventricular arrhythmias that occur in the athlete without structural heart disease are not thought to be life threatening. Athletes with structural heart disease and syncope and those with exertional syncope merit a complete evaluation.

Abstract

When incorporated into tiered therapy implantable cardioverter defibrillators (ICDs), antitachycardia pacing (ATP) techniques have proved useful for termination of sustained monomorphic ventricular tachycardias (VT) and have the advantages of rapid delivery, absence of patient discomfort, and minimal battery drain. The efficacy of low-energy cardioversion (LEC) is similar to that of pacing techniques for VT termination, but LEC has the disadvantages of patient discomfort, atrial proarrhythmia, and greater battery drain compared with ATP. Acceleration of VT occurs with similar frequency with each technique. Neither technique should be used without back-up defibrillation capability in an ICD. VT termination algorithms are currently empiric and require repetitive arrhythmia induction and trials of ATP or LEC. Future studies of the risk and benefits of each technique are likely to define optimal programming strategies in tiered therapy ICDs.